Testing apparatus using charged particles and device manufacturing method using the testing apparatus

ABSTRACT

A substrate is irradiated by primary electrons and secondary electrons generated from the substrate are detected by a detector. A reference die is placed on the stage to obtain a pattern matching template image including feature coordinates of the reference die. A pattern matching is performed with an arbitrary die in a row or column including the reference die using the template image to obtain feature coordinates of the arbitrary die. An angle of misalignment is calculated between the direction of the row or column including the reference die and one of the directions of movement of the substrate on the basis of the feature coordinates of the arbitrary die and those of the reference die. The stage is rotated to correct the angle of misalignment to conform the direction of the row or column including the reference die with the one of the directions of movement of the substrate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No. 12/789,070filed on May 27, 2010, which is a divisional of U.S. application Ser.No. 12/073,892 filed on Mar. 11, 2008, now U.S. Pat. No. 7,741,601,which is a divisional of U.S. application Ser. No. 11/378,465 filed onMar. 20, 2006, now U.S. Pat. No. 7,365,324, which is a divisionalapplication of U.S. application Ser. No. 10/754,623 filed Jan. 12, 2004,now U.S. Pat. No. 7,138,629, which also claims the benefits of priorityfrom Japanese Patent Application Nos. 2003-117014 and 2003-132304 filedon Apr. 22, 2003 and May 9, 2003, respectively, the entire contents ofwhich are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an inspection apparatus inspectingdefects or the like of a pattern formed on the surface of an inspectionobject using an electron beam, and particularly relates to an inspectionapparatus irradiating an electron beam to the inspection object andcapturing secondary electrons modified according to properties of thesurface thereof to form image data, and inspecting in high throughput apattern or the like formed on the surface of the inspection object basedon the image data, and a device production process of producing a devicein a high yield using the inspection apparatus as used for detection ofwafer defects it semiconductor manufacturing. More specifically, thepresent invention relates to a detection apparatus with a projectionelectron microscope system using broad beams, and a device productionprocess using the apparatus.

In a semiconductor process, the design rule is about to move into an eraof 100 nm, and the type of production is now making a transition fromlow variety and large production represented by DRAM to high variety andsmall production found in SOC (Silicon on chip). Accordingly, the numberof production steps increases, improvement in yield for each stepbecomes essential, and inspection of defects coming from the processbecomes important. The present invention relates to an apparatus for usein inspection of a wafer or the like after each step in thesemiconductor process, and relates to an inspection process andapparatus using an electron beam or a device production process usingthe same.

2. Description of the Related Art

As semiconductor devices is highly integrated, and patterns becomesfiner, a high resolution and high throughput inspection apparatus isrequired. For inspecting defects of a wafer substrate having a 100 nmdesign rule, pattern defects or defects of particle vias in wiringhaving a line width of 100 nm or smaller and electric defects thereofshould be observed, and hence a resolution of 100 nm or lower isrequired, and the inspection quantity increases due to an increase inthe number of production steps resulting from high integration of thedevice, and therefore high throughput is required. Furthermore, as thedevice is increasingly multilayered, the inspection apparatus isrequired to have a function of detecting a contact failure (electricdefects) of vias for connection of wiring between layers. Currently,optical defect inspection apparatuses are mainly used, but defectinspection apparatuses using electron beams are expected to gomainstream in stead of the optical defect inspection apparatus in termsof resolution and inspection of contact failure. However, the electronbeam-type defect inspection apparatus has a disadvantage, i.e. it isinferior in throughput to the optical type.

Thus, development of an inspection apparatus having a high resolutionand high throughput and being capable of detecting electric detects isrequired. It is said that the resolution of the optical type is maximum½ of the wavelength of light used, which is equivalent to about 0.2 μmfor commercially practical visible light, for example.

On the other hand, for the type using an electron beam a scanningelectron beam type (SEM type) is usually commercially available, theresolution is 0.1 μm and the inspection time is 8 hours/wafer (200 mmwafer). The electron beam type has a remarkable characteristic such thatelectric defects (breakage of wiring, poor conduction, poor conductionof vias and the like) can be inspected, but the inspection speed is verylow, and development of a defect inspection apparatus performinginspection at a high speed is expected.

Generally, the inspection apparatus is expensive, inferior in throughputto other process apparatuses, and is therefore used after an importantstep, for example, etching, film formation, or CMP (chemical mechanicalpolishing) planarization processing under present circumstances.

The inspection apparatus of the scanning type using an electron beam(SEM) will be described. The SEM type inspection apparatus reduces thesize of an electron beam (the beam diameter corresponds to theresolution), and scans the beam to irradiate a sample in a line form. Onthe other hand, a stage is moved in a direction perpendicular to thescanning direction of the electron beam to irradiate an observation areawith the electron beam in a plain form. The scan width of the electronbeam is generally several hundreds μm. Secondary electrons generatedfrom the sample by irradiation with the size-reduced electron beam(refereed to as primary electron beam) are detected with a detector(scintillator+photomultiplier (photomultiplier tube) or asemiconductor-type detector (PIN diode type) or the like). Coordinatesof the irradiation position and the amount of secondary electrons(signal intensity) are synthesized into an image, and the image isstored in a storage device, or outputted onto a CRT (cathode ray tube).The principle of the SEM (scanning electron microscope) has beendescribed above, and defects of a semiconductor (usually Si) wafer in astep on progress are detected from the image obtained by this process.The inspection speed (corresponding to throughput) depends on the amountof primary electron beams (current value), the beam diameter and theresponse speed of the detector. 0.1 μm of beam diameter (that can beconsidered as resolution), 100 nA of current value and 100 MHz ofdetector response speed are maximum values at present and in this case,it is said that the inspection speed is about 8 hours per wafer having adiameter of 20 cm. The serious problem is that this inspection speed isvery low compared to the optical type ( 1/20 or less of that of theoptical type). Particularly, pattern defects and electric defects of adevice pattern of a design rule of 100 nm or smaller formed on thewafer. i.e. of a line width of 100 nm, a via with the diameter of 100 nmor smaller and the like, and a contaminant of 100 nm or smaller can bedetected at a high speed.

For the SEM-type inspection apparatus described above, the aboveinspection speed is considered as a limit, and a new type of inspectionapparatus is required for further enhancing the speed, i.e. increasingthe throughput.

SUMMARY OF THE INVENTION

For meeting the needs, the present invention provides an electron beamapparatus comprising means for irradiating an electron beam to a sample,means for guiding to a detector electrons obtaining information aboutthe surface of the above described sample by the irradiation of theelectron beam to the above described sample, and means for synthesizingas an image the electrons being guided to the detector and obtaininginformation about the surface of the above described sample.

wherein the illuminance of the above described electron beam in an areaof the above described sample illuminated with the above describedelectron beam is uniform.

The electrons obtaining information about the surface of the abovedescribed sample are desirably at least one of secondary electrons,reflection electrons and back-scatter electrons, or mirror electronsreflected from the vicinity of the surface of the above describedsample.

By the inspection process or inspection apparatus of the presentinvention, defects of a substrate of a wafer or the like having wiringwith the line width of 100 nm or smaller can be inspected.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the overall configuration of a semiconductor inspectionapparatus;

FIG. 2( a) and FIG. 2( b) show the overall configuration of theapparatus of FIG. 1;

FIG. 3 shows the overall configuration of the apparatus of FIG. 1 interms of functions;

FIG. 4 shows main components of an inspection unit of the apparatus ofFIG. 1;

FIG. 5 shows main components of the inspection unit of the apparatus ofFIG. 1;

FIG. 6 shows main components of the inspection unit of the apparatus ofFIG. 1;

FIG. 7 shows main components of the inspection unit of the apparatus ofFIG. 1;

FIG. 8 shows main components of the inspection unit of the apparatus ofFIG. 1;

FIG. 9 shows main components of the inspection unit of the apparatus ofFIG. 1;

FIG. 10 shows main components of the inspection unit of the apparatus ofFIG. 1;

FIG. 11 shows a jacket of the apparatus of FIG. 1;

FIG. 12 shows the jacket of the apparatus of FIG. 1;

FIG. 13 is an elevational view showing main components of thesemiconductor inspection apparatus according to the present invention;

FIG. 14 is a front view showing main components of the semiconductorinspection apparatus according to the present invention;

FIG. 15 shows one example of the configuration of a cassette holder ofthe semiconductor inspection apparatus according to the presentinvention;

FIG. 16 shows the configuration of a mini-environment apparatus of thesemiconductor inspection apparatus according to the present invention;

FIG. 17 shows the configuration of a loader housing of the semiconductorinspection apparatus according to the present invention;

FIG. 18(A) and FIG. 18(B) show the configuration of the loader housingof the semiconductor inspection apparatus according to the presentinvention;

FIGS. 19(A) and 19(B) illustrate an electrostatic chuck for use in thesemiconductor inspection apparatus according to the present invention;

FIG. 20 illustrates the electrostatic chuck for use in the semiconductorinspection apparatus according to the present invention;

FIGS. 20-1(A) and 20-1(B) illustrate another example of theelectrostatic chuck for use in the semiconductor inspection apparatusaccording to the present invention;

FIG. 21 illustrates a bridge tool for use in the semiconductorinspection apparatus according to the present invention;

FIG. 22 illustrates another example of the bridge tool for use in thesemiconductor inspection apparatus according to the present invention;

FIG. 22-1 illustrates the configuration and operation procedures (A) to(C) of an elevator mechanism in a load lock chamber of FIG. 22;

FIG. 22-2 illustrates the configuration and operation procedures (D) to(F) of the elevator mechanism in a load lock chamber of FIG. 22;

FIG. 23 shows an alteration example of a method of supporting a mainhousing in the semiconductor inspection apparatus according to thepresent invention;

FIG. 24 shows an alteration example of the method of supporting a mainhousing in the semiconductor inspection apparatus according to thepresent invention;

FIG. 25-1 shows the configuration of an electro-optic system of aprojection electron microscope type beam inspection apparatus of thesemiconductor inspection apparatus according to the present invention;

FIG. 25-2 shows the configuration of the electro-optic system of thescanning electron beam inspection apparatus of the semiconductorinspection apparatus according to the present invention;

FIG. 25-3 schematically shows one example of the configuration of adetector rotation mechanism of the semiconductor inspection apparatusaccording to the present invention;

FIG. 25-4 schematically shows one example of the configuration of thedetector rotation mechanism of the semiconductor inspection apparatusaccording to the present invention;

FIG. 25-5 schematically shows one example of the configuration of thedetector rotation mechanism of the semiconductor inspection apparatusaccording to the present invention;

FIG. 26 is the first embodiment of the semiconductor inspectionapparatus according to the present invention;

Diagrams (1) to (6) of FIG. 27-1 each illustrate a shape of a sampleirradiating beam;

Diagrams (1-1) to (4) of FIG. 27-2 each illustrate an irradiation formof a linear beam;

FIG. 28 illustrates secondary electrons being taking out from a columnin the semiconductor inspection apparatus according to the presentinvention;

FIG. 29 shows the second embodiment of the semiconductor inspectionapparatus according to the present invention;

FIG. 30 shows the third embodiment of the semiconductor inspectionapparatus according to the present invention;

FIG. 31 shows the fourth embodiment of the semiconductor inspectionapparatus according to the present invention;

FIG. 32 shows the fifth embodiment of the semiconductor inspectionapparatus according to the present invention;

FIG. 33 illustrates an irradiation area covering an observation area;

FIG. 34 illustrates the irradiation form and irradiation efficiency;

FIG. 35 shows the sixth embodiment of the semiconductor inspectionapparatus according to the present invention, and shows theconfiguration of a detection system using a relay lens;

FIG. 36 shows the sixth embodiment of the semiconductor inspectionapparatus according to the present invention, and shows theconfiguration of a detection system using an FOP;

FIGS. 37(A) and 37(B) show the eighth embodiment of the semiconductorinspection apparatus according to the present invention;

FIG. 38 is a graph showing dependency of the transmittance on thediameter of an opening;

FIG. 39 shows a specific example of an electron detection system in theapparatus of FIG. 37;

FIGS. 40(A) and (B) illustrate requirements for operating the electrondetection system in the apparatus of FIG. 37 in three modes;

FIG. 41 shows the configuration of an E×B unit of the semiconductorinspection apparatus according to the present invention;

FIG. 42 is a sectional view along the line A of FIG. 41;

FIG. 43 shows the ninth embodiment of the semiconductor inspectionapparatus according to the present invention;

FIG. 44 shows simulation of an electric field distribution;

FIG. 45 shows the configuration of a power supply unit of thesemiconductor inspection apparatus according to the present invention;

FIG. 46 shows a circuit system generating a direct-current voltage inthe power supply unit shown in FIG. 45;

FIG. 47 shows one example of the circuit configuration of a staticbipolar power supply of the power supply unit shown in FIG. 45;

FIG. 48 shows a special power supply in the power supply unit shown inFIG. 45;

FIG. 49 shows a special power supply in the power supply unit shown inFIG. 45;

FIG. 50 shows a special power supply in the power supply unit shown inFIG. 45;

FIG. 51 shows one example of a power supply circuit for a retardingchuck in the power supply unit shown in FIG. 45;

FIG. 52 shows one example of the hardware configuration of an EOcorrecting deflection voltage in the power supply unit shown in FIG. 45;

FIG. 53 shows one example of the circuit configuration of an octupoleconversion unit in the power supply unit shown in FIG. 45;

FIG. 54(A) shows one example of the circuit configuration of ahigh-speed and high-voltage amplifier in the power supply unit shown inFIG. 45, and FIG. 54(B) shows an output waveform;

FIG. 55 shows the first embodiment of a precharge unit of thesemiconductor inspection apparatus shown in FIG. 13;

FIG. 56 shows the second embodiment of a precharge unit of thesemiconductor inspection apparatus shown in FIG. 13;

FIG. 57 shows the third embodiment of a precharge unit of thesemiconductor inspection apparatus shown in FIG. 13;

FIG. 58 shows the fourth embodiment of a precharge unit of thesemiconductor inspection apparatus shown in FIG. 13;

FIG. 59 shows an imaging apparatus comprising the precharge unit shownin FIGS. 55 to 58;

FIG. 60 illustrates the operation of the apparatus of FIG. 59;

FIG. 61 shows another example of configuration of a defect inspectionapparatus comprising the precharge unit;

FIG. 62 shows an apparatus for converting a secondary electron imagesignal into an electric signal in the apparatus shown in FIG. 61;

FIG. 63 is a flow chart illustrating the operation of the apparatusshown in FIG. 61;

FIGS. 64( a), 64(b) and 64(c) show a method for detecting defects in theflow chart of FIG. 63;

FIG. 65 shows another example of configuration of the defect inspectionapparatus comprising the precharge unit;

FIG. 66 shows still another example of configuration of the defectinspection apparatus comprising the precharge unit;

FIG. 67 illustrates the operation of a control system of thesemiconductor inspection apparatus according to the present invention;

FIG. 68 illustrates the operation of the control system of thesemiconductor inspection apparatus according to the present invention;

FIG. 69 illustrates the operation of the control system of thesemiconductor inspection apparatus according to the present invention;

FIG. 70 illustrates the operation of the control system of thesemiconductor inspection apparatus according to the present invention;

FIG. 71 illustrates the operation of the control system of thesemiconductor inspection apparatus according to the present invention;

FIG. 72 illustrates the operation of the control system of thesemiconductor inspection apparatus according to the present invention;

FIG. 73 illustrates the operation of the control system of thesemiconductor inspection apparatus according to the present invention;

FIG. 74 illustrates an alignment procedure in the semiconductorinspection apparatus according to the present invention;

FIG. 75 illustrates the alignment procedure in the semiconductorinspection apparatus according to the present invention;

FIG. 76 illustrates the alignment procedure in the semiconductorinspection apparatus according to the present invention;

FIG. 77 illustrates a defect inspection procedure in the semiconductorinspection apparatus according to the present invention;

FIG. 78 illustrates the defect inspection procedure in the semiconductorinspection apparatus according to the present invention;

FIG. 79 illustrates the defect inspection procedure in the semiconductorinspection apparatus according to the present invention;

FIGS. 80(A) and 80(B) illustrate the defect inspection procedure in thesemiconductor inspection apparatus according to the present invention;

FIG. 81 illustrates the defect inspection procedure in the semiconductorinspection apparatus according to the present invention;

FIG. 82 illustrates the defect inspection procedure in the semiconductorinspection apparatus according to the present invention;

FIG. 83(A) and FIG. 83(B) illustrate the defect inspection procedure inthe semiconductor inspection apparatus according to the presentinvention;

FIG. 84 illustrates the configuration of the control system in thesemiconductor inspection apparatus according to the present invention;

FIG. 85 illustrates the configuration of a user interface in thesemiconductor inspection apparatus according to the present invention;

FIG. 86 illustrates the configuration of a user interface in thesemiconductor inspection apparatus according to the present invention;

FIG. 87 illustrates another function and configuration of thesemiconductor inspection apparatus according to the present invention;

FIG. 88 shows an electrode in another function and configuration of thesemiconductor inspection apparatus according to the present invention;

FIG. 89 shows the electrode in another function and configuration of thesemiconductor inspection apparatus according to the present invention;

FIG. 90 is a graph showing a voltage distribution between the wafer andan objective lens;

FIG. 91 is a flow chart illustrating the secondary electron detectionoperation in another function and configuration of the semiconductorinspection apparatus according to the present invention;

FIG. 92 shows a potential application mechanism in the apparatus shownin FIG. 91;

FIGS. 93(A) and 93(B) illustrate an electron beam calibration method inthe apparatus shown in FIG. 91;

FIG. 94 illustrates an alignment control method in the apparatus shownin FIG. 91;

FIGS. 95(A) and 95(B) illustrate a concept of EO correction in theapparatus shown in FIG. 92;

FIG. 96 illustrates the specific apparatus configuration for EOcorrection in the apparatus shown in FIG. 92;

FIGS. 97(A) and 97(B) illustrate EO correction in the apparatus shown inFIG. 92;

FIG. 98 illustrates EO correction in the apparatus shown in FIG. 92;

FIG. 99 illustrates EO correction in the apparatus shown in FIG. 92;

FIG. 100 illustrates EO correction in the apparatus shown in FIG. 92;

FIG. 101 illustrates the idea of a TDI transfer clock.

FIG. 102 illustrates the idea of the TDI transfer clock;

FIG. 103 is a timing chart illustrating the operation of the circuit ofFIG. 102;

FIG. 104 shows an alteration example of the defect inspection apparatusaccording to the present invention;

FIG. 105 is a flow chart illustrating the operation of the apparatusshown in FIG. 104;

FIG. 106 is a flow chart illustrating the operation of the apparatusshown in FIG. 104;

FIG. 107 is a flow chart illustrating the operation of the apparatusshown in FIG. 104;

FIG. 108 illustrates the operation of the apparatus shown in FIG. 104;

FIG. 109 illustrates the operation of the apparatus shown in FIG. 104;

FIG. 110 illustrates a semiconductor device production process accordingto the present invention;

FIG. 111 illustrates the semiconductor device production processaccording to the present invention;

FIG. 112 illustrates an inspection procedure of the semiconductor deviceproduction process according to the present invention;

FIG. 113 illustrates a basic flow of the inspection procedure of thesemiconductor device production process according to the presentinvention;

FIG. 114 shows a setting of an inspection object die;

FIG. 115 illustrates a setting of an inspection area in the die.

FIG. 116 illustrates the inspection procedure of the semiconductordevice production process according to the present invention;

FIGS. 117(A) and 117(B) illustrate the inspection procedure of thesemiconductor device production process according to the presentinvention;

FIG. 118-1 shows an example of scanning where there is one inspectiondie in the inspection procedure in the semiconductor device productionprocess according to the present invention;

FIG. 118-2 shows one example of the inspection die;

FIG. 119 illustrates a method for generating a reference image in theinspection procedure of the semiconductor device production processaccording to the present invention;

FIG. 120 illustrates an adjacent die comparison method in the inspectionprocedure of the semiconductor device production process according tothe present invention;

FIG. 121 illustrates the adjacent die comparison method in theinspection procedure of the semiconductor device production processaccording to the present invention;

FIG. 122 illustrates a reference die comparison method in the inspectionprocedure of the semiconductor device production process according tothe present invention;

FIG. 123 illustrates the reference die comparison method in theinspection procedure of the semiconductor device production processaccording to the present invention;

FIG. 124 illustrates the reference die comparison method in theinspection procedure of the semiconductor device production processaccording to the present invention;

FIG. 125 illustrates focus mapping in the inspection procedure of thesemiconductor device production process according to the presentinvention;

FIG. 126 illustrates focus mapping in the inspection procedure of thesemiconductor device production process according to the presentinvention;

FIG. 127 illustrates focus mapping in the inspection procedure of thesemiconductor device production process according to the presentinvention;

FIG. 128 illustrates focus mapping in the inspection procedure of thesemiconductor device production process according to the presentinvention;

FIG. 129 illustrates focus mapping in the inspection procedure of thesemiconductor device production process according to the presentinvention;

FIG. 130 illustrates focus mapping in the inspection procedure of thesemiconductor device production process according to the presentinvention;

FIG. 131 illustrates litho-margin measurement in the inspectionprocedure of the semiconductor device production process according tothe present invention;

FIG. 132 illustrates litho-margin measurement in the inspectionprocedure of the semiconductor device production process according tothe present invention;

FIG. 133 illustrates litho-margin measurement in the inspectionprocedure of the semiconductor device production process according tothe present invention;

FIG. 134 illustrates litho-margin measurement in the inspectionprocedure of the semiconductor device production process according tothe present invention;

FIG. 135 illustrates litho-margin measurement in the inspectionprocedure of the semiconductor device production process according tothe present invention;

FIG. 136 illustrates litho-margin measurement in the inspectionprocedure of the semiconductor device production process according tothe present invention;

FIG. 137 illustrates litho-margin measurement in the inspectionprocedure of the semiconductor device production process according tothe present invention;

FIG. 138 shows one example of a stage apparatus in the semiconductorinspection apparatus according to the present invention;

FIG. 139 shows one example of the stage apparatus in the semiconductorinspection apparatus according to the present invention;

FIG. 140 shows one example of the stage apparatus in the semiconductorinspection apparatus according to the present invention;

FIG. 141 shows another example of the stage apparatus in thesemiconductor inspection apparatus according to the present invention;

FIG. 142 shows another example of the stage apparatus in thesemiconductor inspection apparatus according to the present invention;

FIG. 143 shows still another example of the stage apparatus in thesemiconductor inspection apparatus according to the present invention;

FIG. 144 shows still another example of the stage apparatus in thesemiconductor inspection apparatus according to the present invention;

FIG. 145 shows another example of the stage apparatus in thesemiconductor inspection apparatus according to the present invention;

FIG. 146 shows another example of the stage apparatus in thesemiconductor inspection apparatus according to the present invention;

FIG. 147 shows another example of the stage apparatus in thesemiconductor inspection apparatus according to the present invention;

FIGS. 148(A) and 148(B) show a conventional stage apparatus;

FIG. 149 shows an optical system and a detector in the semiconductorinspection apparatus according to the present invention;

FIGS. 150( a) and 150(b) show another embodiment of the semiconductorinspection apparatus according to the present invention;

FIG. 151 shows the electron beam apparatus of FIG. 150 in detail;

FIG. 152 shows a primary electron irradiation method in thesemiconductor inspection apparatus according to the present invention;

FIG. 153 shows an embodiment of the semiconductor inspection apparatusaccording to the present invention, with a structure of an electrode forpreventing insulation breakdown;

FIG. 154 is a table illustrating the operation of the apparatus of FIG.153;

FIG. 155 shows the structure of the electrode in the apparatus of FIG.153;

FIG. 156 shows the structure of the electrode in the apparatus of FIG.153;

FIG. 157 shows the structure of the electrode in the apparatus of FIG.153;

FIG. 158 shows the structure of the electrode in the apparatus of FIG.153;

FIG. 159 shows the embodiment of the semiconductor inspection apparatusaccording to the present invention, which comprises an anti-vibrationapparatus;

FIGS. 160( a) to 160 (c) illustrate the apparatus of FIG. 159;

FIG. 161 illustrates the apparatus of FIG. 159;

FIG. 162 illustrates the apparatus of FIG. 159;

FIG. 163 illustrates the apparatus of FIG. 159;

FIGS. 164( a) to 164(c) illustrate a pattern matching process in theapparatus of FIG. 159;

FIG. 165 illustrates the holding of the wafer in the semiconductorinspection apparatus according to the present invention;

FIG. 166 illustrates the holding of the wafer in the semiconductorinspection apparatus according to the present invention;

FIGS. 167( a) and 167(b) illustrate the holding of the wafer in thesemiconductor inspection apparatus according to the present invention;

FIG. 168 shows the electron beam apparatus comprising a chuckillustrated in FIG. 166;

FIG. 169 shows an E×B separator in the apparatus shown in FIG. 168;

FIG. 170 shows the E×B separator in the apparatus shown in FIG. 168;

FIG. 171 shows the embodiment in which the inspection apparatusaccording to the present invention is connected to a production line;

FIG. 172(A) schematically shows the embodiment of a projection electronmicroscope type apparatus capable of using secondary electrons andreflection electrons selectively;

FIG. 172(B) schematically shows the configuration of a secondary opticalsystem of the apparatus;

FIG. 173 shows the specific configuration of a secondary electrondetection system in FIG. 172(A);

FIGS. 174(A) and 174(B) illustrate different operation modes of thedefect inspection apparatus shown in FIG. 172(A);

FIG. 175 shows the specific configuration of a lens of the secondaryoptical system of the defect inspection apparatus shown in FIG. 172(A);

FIG. 176(A) schematically shows the configuration of an alterationexample of the projection electron microscope type apparatus shown inFIG. 172(A);

FIG. 176(B) illustrates a scan method of the apparatus shown in FIG.176(A);

FIG. 177(A) schematically shows the configuration of another example ofthe projection electron microscope type apparatus shown in FIG. 172(A);

FIG. 177(B) illustrates the scan method of the apparatus shown in FIG.177(A);

FIG. 178 shows the structure of a vacuum chamber and XY stage of theprojection electron microscope type apparatus shown in FIG. 172(A), andan inert gas circulation pipe system therefor;

FIG. 179 shows one example of a differential pumping mechanism in FIG.178; and

FIG. 180 schematically shows the configuration of an entire inspectionsystem.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of semiconductor inspection apparatus according to thepresent invention will be described in detail below with reference tothe drawings in the following order.

Description

1. Overall configuration

1-1) Main chamber, stage, jacket of vacuum transportation system

-   -   1-1-1) Active vibration removal table    -   1-1-2) Main chamber    -   1-1-3) XY stage

1-2) Laser interference measurement system

1-3) Inspection unit jacket

2. Embodiments

2-1) Transportation system

-   -   2-1-1) Cassette holder    -   2-1-2) Mini-environment apparatus    -   2-1-3) Main housing    -   2-1-4) Loader housing    -   2-1-5) Loader    -   2-1-6) Stage apparatus    -   2-1-7) Wafer chucking mechanism        -   2-1-7-1) Basic structure of electrostatic chuck        -   2-1-7-2) Chucking mechanism for 200/300 bridge tool        -   2-1-7-3) Wafer chucking procedure    -   2-1-8) Apparatus configuration for 200/300 bridge tool

2-2) Method for transportation of wafer

2-3) Electro-optical system

-   -   2-3-1) Overview    -   2-3-2) Details of configuration        -   2-3-2-1) Electron gun (electron beam source)        -   2-3-2-2) Primary optical system        -   2-3-2-3) Secondary optical system    -   2-3-3) E×B unit (Wien filter)    -   2-3-4) Detector    -   2-3-5) Power supply

2-4) Precharge unit

2-5) Vacuum pumping system

2-6) Control system

-   -   2-6-1) Configuration and function    -   2-6-2) Alignment procedure    -   2-6-3) Defect inspection    -   2-6-4) Control system configuration    -   2-6-5) User interface configuration

2-7) Descriptions of other functions and configurations

-   -   2-7-1) Control electrode    -   2-7-2) Potential application method    -   2-7-3) Electron beam calibration method    -   2-7-4) Cleaning of electrode    -   2-7-5) Alignment control method    -   2-7-6) EO correction    -   2-7-7) Image comparison method    -   2-7-8) Device production process    -   2-7-9) Inspection

2-8) Inspection process

-   -   2-8-1) Overview    -   2-8-2) Inspection algorithm        -   2-8-2-1) Array inspection        -   2-8-2-2) Random inspection        -   2-8-2-3) Focus mapping        -   2-8-2-4) litho-margin measurement            3. Other embodiments

3-1) Alteration example of stage apparatus

3-2) Other embodiments of electron beam apparatus

-   -   3-2-1) Electron gun (electron beam source)    -   3-2-2) Structure of electrode

3-3) Embodiment for anti-vibration apparatus

3-4) Embodiment for wafer holding

3-5) Embodiment of E×B separator

3-6) Embodiment of production line

3-7) Embodiment using other electrons

3-8) Embodiment using secondary electrons and reflection electrons

1. Overall Configuration

First, the overall configuration of the semiconductor inspectionapparatus will be described.

The overall configuration of the apparatus will be described usingFIG. 1. The apparatus is comprised of an inspection apparatus main body,a power supply rack, a control rack, an image processing unit, a filmformation apparatus, an etching apparatus and the like. A roughingvacuum pump such as a dry pump is placed outside a clean room. The mainpart of the interior of the inspection apparatus main body is comprisedof an electron beam optical column, a vacuum transportation system, amain housing containing a stage, a vibration removal table, aturbo-molecular pump and the like as shown in FIG. 2( a) and FIG. 2( b).

A control system comprises two CRTs and an instruction input feature(keyboard or the like). FIG. 3 shows a configuration from a viewpoint ofa function. The electron beam column is mainly comprised of anelectro-optical system, detection system, an optical microscope and thelike. The electro-optical system is comprised of a lens and the like,and a transportation system is comprised of a vacuum transportationrobot, an atmospheric transportation robot, a cassette loader, variouskinds of position sensors and the like.

Here, the film formation apparatus and etching apparatus, and a cleaningapparatus (not shown) are placed side by side near the inspectionapparatus main body, but they may be incorporated in the inspectionapparatus main body. They are used, for example, for inhibiting thecharge of a sample or cleaning the surface of the sample. If asputtering system is used, one apparatus may have functions of both filmformation and etching apparatuses.

Although not shown in the figures, associated apparatuses may be placedside by side near the inspection apparatus main body, or may beincorporated in the inspection apparatus main body depending on thepurpose of use. Alternatively, the inspection apparatus may beincorporated in the associated apparatus. For example, achemical-mechanical polishing apparatus (CMP) and the cleaning apparatusmay be incorporated in the inspection apparatus main body, or a CVD(chemical vapor deposition) apparatus may be incorporated in theinspection apparatus and in this case, there are advantages that theinstallation area and the number of units for transportation of samplescan be reduced, and transportation time can be shortened, and so on.

Similarly, the film formation apparatus such as a plating apparatus maybe incorporated in the inspection apparatus main body. Similarly, theinspection apparatus may be used in conjunction with a lithographyapparatus.

1-1) Main Chamber, Stage, Jacket of Vacuum Transportation System

In FIGS. 4, 5 and 6, main components of an inspection unit of thesemiconductor inspection apparatus are shown. The inspection unit of thesemiconductor inspection apparatus comprises an active vibration removaltable 4•1 for shutting off vibration from the outside environment, amain chamber 4•2 as an inspection chamber, an electro-optical apparatus4•3 placed on the main chamber, an XY stage 5•1 for scanning the waferplaced in the main chamber, a laser interference measurement system 5•2for control of the motions of the XY stage, and a vacuum transportationsystem 4•4 accompanying the main chamber, and they are placed inpositional relations shown in FIGS. 4 and 5. The inspection unit of thesemiconductor inspection apparatus further comprises a jacket 6•1 forallowing environmental control and maintenance of the inspection unit,and is placed in positional relations shown in FIG. 6.

1-1-1) Active Vibration Removal Table

The active vibration removal table 4•1 has a weld platen 5•4 mounted onan active vibration removal unit 5•3, and the main chamber 4•2 as aninspection chamber, the electro-optical apparatus 4•3 placed on the mainchamber, the vacuum transportation system 4•4 accompanying the mainchamber and the like are held on the weld platen. In this way,vibrations in the inspection unit from the external environment can beinhibited. In this embodiment, the natural frequency is within ±25% of 5Hz in the X direction, 5 Hz in the Y direction and 7.6 Hz in the Zdirection, and the control performance is such that the transmissionlevel of each axis is 0 dB or smaller at 1 Hz, −6.4 dB or smaller at 7.6Hz, −8.6 dB or smaller at 10 Hz and −17.9 dB or smaller at 20 Hz (allunder no load on the platen). In another structure of the activevibration removal table, the main chamber, the electro-optical apparatusand the like are suspended to be held. In still another structure, stoneplaten is mounted to hold the main chamber and the like.

1-1-2) Main Chamber

The main chamber 4•2 directly holds a turbo-molecular pump 7•2 in thelower part to achieve a certain degree of vacuum (10⁻⁴ Pa or lower) inthe inspection environment, and comprises therein a high accuracy XYstage 5•1 for scanning the wafer, so that a magnetic force from outsidecan be blocked. In this embodiment, the following structure is providedto improve the flatness of the holding surface of the high accuracy XYstage wherever possible. A lower plate 7•3 of the main chamber is placedand fixed on an especially high flatness area 7•4 (flatness of 5 μm orless in this embodiment) prepared on the weld platen. Further, a middleplate is provided as a stage holding surface in the main chamber. Themiddle plate is supported at three points against the lower plate of themain chamber, so that it is not directly affected by the flatness of thelower plate. In this embodiment, a support part consists of a sphericalseat 7•6. The middle plate is capable of achieving a flatness of thestage holding surface at 5 μm or less when loaded with the self-weightand the weight of the stage. Furthermore, to alleviate the effect ofdeformation of the main chamber by a change in internal pressure (fromatmospheric pressure to reduced pressure of 10⁻⁴ Pa or lower) on thestage holding surface, the middle plate is fixed directly on the weldplaten at near the three points at which the middle plate is supportedon the lower plate.

To accurately control the XY stage, a measurement system with a laserinterferometer at a stage position is installed. An interferometer 8•1is placed under vacuum to inhibit a measurement error, and is fixeddirectly on a high-rigidity chamber wall 7•7 in this embodiment toreduce vibrations of the interferometer causing directly a measurementerror as small as 0. Furthermore, to eliminate errors of the measurementposition and the inspection position, the extended line of themeasurement area by the interferometer matches the inspection area asaccurately as possible. Furthermore, a motor 8•2 for XY motions of thestage is held by the chamber wall 7•7 in this embodiment, but if it isnecessary that the effect of motor vibrations on the main chamber isfurther inhibited, the motor 8•2 is held by the weld platen 7•1directly, and mounted on the main chamber in a structure nottransferring vibrations of a bellow and the like.

The main chamber 4•2 is composed of a material having a high magneticpermeability to block the effect of an external magnetic field on theinspection area. In this embodiment, the main chamber 4•2 has permalloyand iron such as SS 400 plated with Ni as an anticorrosive coating. Inanother embodiment, permendur, super permalloy, electromagnetic softiron, pure iron or the like is used. Further, it is effective to coverthe periphery of the inspection area in the chamber directly with amaterial having a high magnetic permeability as a magnetic shieldingeffect.

1-1-3) XY Stage

The XY stage 5•1 can scan the wafer with high accuracy under vacuum.Strokes of X and Y are each 200 to 300 mm for the 200 mm wafer, and 300to 600 mm for the 300 mm wafer. In this embodiment, the XY stage isdriven by the motor 8•2 for driving X and Y axes fixed on the mainchamber wall, and a ball screw 8•5 attached thereto via a magnetic fluidseal 8•3. In this embodiment, since the XY motions can be performed in astate in which the ball screw for driving X and Y is fixed to thechamber wall, the stage structure is as follows.

First, in the lower stage, an Y stage 7•10 is placed, and a ball screw7•8 for driving and a cross roller guide 7•11 are installed. On the Ystage, a middle stage 7•12 having thereon a ball screw 7•14 for drivingthe X axis is placed, and an X stage 7•13 is mounted thereon. The middlestage and the Y stage and x stage are connected together along the Yaxis by the cross roller guide. In this way, when the Y axis is shifted,the X stage is moved by the Y stage and the connection area 7•14, andthe middle stage remains fixed. Another embodiment has a two-stagestructure in which the middle stage is aligned with the upper stageaxis. Furthermore, in the XY stage of another embodiment, the XY stageitself is driven by a linear motor. Further, a high-accuracy mirror 8•4(the flatness is λ/20 or less, and the material is aluminum-depositedsynthetic quartz) is installed so that measurements can be made over theentire stroke by the interferometer.

Furthermore, a θ stage 7•15 is placed on the XY stage for performingwafer alignment under vacuum. In the θ stage in this embodiment, twoultrasonic motors are placed for driving, and a linear scale is placedfor position control. Various cables connected to movable partsperforming X, Y and θ motions are clamped by cable bears each held onthe X stage and the Y stage, and connected to the outside of the mainchamber via a field-through provided on the chamber wall.

Specifications of this embodiment with the above structures are shown inTables 1 and 2.

TABLE 1 Table specifications and characteristics No. Items CriteriaInspection process 1 X axis positioning ±3 [μm] or less Measurement bylaser length measuring repeatability (graphical representation) machinefor delivery inspection with Y axis at center 2 Y axis positioning ±3[μm] or less Measurement by laser length measuring repeatability(graphical representation) machine for delivery inspection with X axisat center 3 θ positioning ±0.4 [sec] (±2 pulses) or less Measurement bydeviation pulses at the time repeatability (target) of stopping ofrotation sensor. (numerical indication) Measurements are made at threepoints of 0°, 1° and +1° 4 X axis positioning ±20 [μm] or lessMeasurement by laser length measuring accuracy (graphicalrepresentation) machine for delivery inspection with Y axis at center 5Y axis positioning ±20 [μm] or less Measurement by laser lengthmeasuring accuracy (graphical representation) machine for deliveryinspection with X axis at center 6 X axis backlash ±1 [μm] or lessMeasurement by laser length measuring (numerical indication) machine fordelivery inspection with Y axis at center 7 X axis backlash ±1 [μm] orless Measurement by laser length measuring (numerical indication)machine for delivery inspection with X axis at center 8 X axis pitching5 [sec] or less (target) Measurement by laser length measuring(graphical representation) machine for delivery inspection with Y axisat center and both ends 9 Y axis pitching 5 [sec] or less (target)Measurement by laser length measuring (graphical representation) machinefor delivery inspection with X axis at center and both ends 10 X axisyawing 5 [sec] or less (target) Measurement by laser length measuring(graphical representation) machine for delivery inspection with Y axisat center and both ends 11 Y axis pitching 5 [sec] or less (target)Measurement by laser length measuring (graphical representation) machinefor delivery inspection with X axis at center and both ends 12 X axisrolling Reference value Measurement of Y axis length measuring(graphical representation) mirror by automatic collimater with Y axis atcenter 13 Y axis rolling Reference value Measurement of X axis lengthmeasuring (graphical representation) mirror by automatic collimater withX axis at center 14 Vertical straightness ±2 [μm] or less Measurement bystraight master and ADE (graphical representation) displacement meter.Measurements are on the cross at the center and reference values are atboth ends 15 Orthogonality of X 10 [μm] or less Measurement byorthogonality master and and Y axes (numerical indication) dial gage 16Distance between 1 ± 0.5 [mm] Measurement by positioning laser lengthORG switch and (numerical indication) measuring machine motor startingpoint

TABLE 2 System specifications and characteristics No. Items CriteriaInspection process 1. X axis lateral ±0.5 μm or less Y axis-X axisdeviation during displacement @10 mm/sec, @15 mm/sec movement from 0 to20 mm at ±1.0 μm or less 20 mm/sec, with Y axis at center @30 mm/sec±2.0 μm or less @60 mm/sec (excluding chamber vibration componentsduring acceleration and deceleration) (graphical representation) 2. Xaxis positioning ±0.5 μm or less Stop accuracy after movement accuracy(graphical representation) from 0 to 20 mm at 20 mm/sec, with Y axis atcenter 3. Y axis positioning ±0.5 μm or less Stop accuracy aftermovement accuracy (graphical representation) from 0 to 20 mm at 20mm/sec, with X axis at center 4. Y axis positioning ±3.0 μm or lessdeviational variation after accuracy @10 mm/sec, @15 mm/sec movement atconstant speed, with ±5.0 μm or less x axis at center @30 mm/sec. @60mm/sec (graphical representation)

1-2) Laser Interference Measurement System

The laser interference measurement system is comprised of a laseroptical system having an optical axis which is parallel to X and Y axesand has an inspection position on its extended line, and aninterferometer 8•1 placed therebetween. The optical system in thisembodiment is placed in positional relations shown in FIGS. 9 and 10.Laser light emitted from a laser 9•1 placed on the weld platen iserected upright by a bender 9•2, and then bent to be parallel with ameasurement plane by a bender 10•1. Further, the laser light is splitinto light for X axis measurement and light for Y axis measurement by asplitter 9•4, then bent to be parallel with the Y axis and the X axis bya bender 10•3 and a bender 9•6, respectively, and guided into the mainchamber.

An adjustment method in starting the optical system will be describedbelow. First, an adjustment is made so that laser light emitted from thelaser is bent perpendicularly by the bender 9•2, and bent horizontallyby the bender 10•1. Then, the bender 10•3 is adjusted so that an opticalaxis of light bent by the bender 10•3 and reflected by a mirror 8•4placed accurately perpendicularly to the Y axis and returned perfectlymatches an optical axis of incident light. By making an observation ofthe optical axis just behind the laser with the interferometer removedso as not to interrupt reflected light, an accurate adjustment can bemade. Furthermore, the optical axis adjustment of the X axis can beperformed independently with the splitter 9•4 and the bender 9•6 afterperforming the optical axis adjustment of the Y axis. The adjustment canbe performed as that of the Y axis. Further, after the axes of incidentlight and reflected light of the X axis and the Y axis are adjusted, theintersection point of the optical axes (assuming that no mirror exists)should be made to match the wafer inspection position. As a result, abracket fixing the bender 10•3 can move perpendicularly to the Y axis,and a bracket fixing the bender 9•6 can move perpendicularly to the Xaxis with incident light and reflected light perfectly matching eachother. Further, the bender 10•1, the splitter 9•4, the bender 10•3 andthe bender 9•6 can desirably move vertically while retaining theirrespective positional relations.

Furthermore, a method for adjustment of optical axes associated withreplacement of the laser in the apparatus in operation after initiationwill be described below. In the apparatus in operation in which theinside of the main chamber is kept under vacuum, the optical axis or thelike having an interferometer removed has a difficulty. Thus, a tool forplacing targets 10•2 at several points on an optical path outside themain chamber so that the optical path in the start can be assessed onlyoutside the main chamber is prepared. After replacement of the laser,the adjustment made in the start can be reproduced by adjusting theoptical axis with respect to the target 10•2 only with an adjustmentfeature provided on a laser mounting seat.

1-3) Inspection Unit Jacket

An inspection unit jacket 4•7 can be provided with a feature as a flamestructure for maintenance. In this embodiment, a containable twin crane11•1 is provided on the upper part. The crane 11•1 is mounted on atraverse rail 11•2, and the traverse rail is placed on a traveling rail(longitudinal) 11•3. The traveling rail is usually housed as shown inFIG. 11, during maintenance, the traveling rail rises as shown in FIG.12, so that the stroke in the vertical direction of the crane can beincreased. Consequently, an electro-optical apparatus 4•3, a mainchamber top plate and the XY stage 5•1 can be attached to/detached fromthe back face of the apparatus by the crane included in the jacketduring maintenance. Another embodiment of the crane included in thejacket has a crane structure having a rotatable open-sided axis.

Furthermore, the inspection unit jacket can also have a function as anenvironment chamber. This has an effect of magnetic shielding along withcontrol of temperature and humidity as required.

2. Embodiments

Preferred embodiments of the present invention will be described belowas a semiconductor inspection apparatus inspecting a substrate, i.e. awafer having a pattern formed on the surface as an inspection object,with reference to the drawings.

2-1) Transportation System

FIGS. 13 and 14 show main components of the semiconductor inspectionapparatus according to the present invention with an elevational viewand a front view. This semiconductor inspection apparatus 13•1 comprisesa cassette holder 13•2 holding cassettes each containing a plurality ofwafers, a mini-environment apparatus 13•3, a loader housing 13•5constituting a working chamber, a loader 13•7 loading the wafer from thecassette holder 13•2 to a stage apparatus 13•6 placed in a main housing13•4, and an electro-optical apparatus 13•8 placed in a vacuum housing,and they are placed in positional relations shown in FIGS. 13 and 14.

The semiconductor inspection apparatus 13•1 further comprises aprecharge unit 13•9 placed in the vacuum main housing 13•4, a potentialapplication mechanism applying a potential to the wafer, an electronbeam calibration mechanism, and an optical microscope 13•11 constitutingan alignment control apparatus 13•10 for positioning the wafer on thestage apparatus.

2-1-1) Cassette Holder

The cassette holder 13•2 holds a plurality of cassettes 13•12 (twocassettes in this embodiment) (e.g. closed cassettes such as SMIF andFOUP manufactured by Assist Co. Ltd.) each containing a plurality ofwafers (e.g. 25 wafers) housed with arranged vertically in parallel. Thecassette holder 13•2 may be freely selected and placed such that ifcassettes are conveyed by a robot or the like and automatically loadedinto the cassette holder 13•2, the cassette holder 13•2 having astructure suitable for this arrangement is selected, and if cassettesare manually loaded, the cassette holder having an open cassettestructure suitable for this arrangement is selected. In this embodiment,the cassette holder 13•2 has a form in which the cassettes 13•12 areautomatically loaded, and for example, a lift table 13•13, and a liftmechanism 13•14 vertically moving the lift table 13•13, wherein thecassette 13•12 can be automatically set on the lift table 13•13 in astate shown by a chain line in FIG. 14, and after the cassette 13•12 isset, it is automatically rotated to a state shown by a solid line inFIG. 14, and directed to a rotation axis line of a first transportationunit in the mini-environment apparatus.

Furthermore, the lift table 13•13 is descended to a state shown by achain line in FIG. 13. In this way, a cassette holder having a wellknown structure may be used as appropriate for any of the cassetteholder to be used when the cassette is automatically loaded and thecassette holder when the cassette is manually loaded, and detaileddescriptions of their structures and functions are not presented.

In another embodiment, as shown in FIG. 15, a plurality of 300 mmsubstrates are housed in a trench pocket (not described) fixed in a boxmain body 15•1, and are conveyed, stored and so on. A substratetransportation box 15•2 is comprised of the prismatic box main body15•1, a substrate loading/unloading door 15•3 communicating with asubstrate loading/unloading door automatic opening/closing apparatus sothat an opening on the side face of the box main body 15•1 can bemechanically opened and closed, a lid 15•4 located opposite to theopening and covering openings for attachment and detachment of filtersand a fan motor, the trench pocket (not shown) for holding a substrate W(FIG. 13), an ULPA filter 15•5, a chemical filter 15•6 and a fan motor15•7. In this embodiment, substrates are loaded/unloaded by a robot-typefirst transportation unit 15•7 of the loader 13•7.

Furthermore, the substrate or wafer housed in the cassette 13•12 is tobe inspected, and such inspection is performed after or during a processof processing the wafer during the semiconductor production step.Specifically, the substrate or wafer undergoing a film formation step,CMP, ion implantation and the like, the wafer having a wiring patternformed on the surface, or the wafer having no wiring pattern yet formedon the surface is housed in the cassette. For the wafer housed in thecassette 12•12, a large number of wafers are spaced vertically andarranged in parallel, and therefore an arm of the first transportationunit can be moved vertically so that they can be held by the wafer atany position and the first transportation unit described later.Furthermore, the cassette is provided with a feature for controlling amoisture content in the cassette to prevent oxidization and the like ofthe wafer surface after the process. For example, a dehumidifying agentsuch as silica gel is placed in the cassette, in this case, anydehumidifying agent having an effect of dehumidification may be used.

2-1-2) Mini-Environment Apparatus

In FIGS. 13 to 16, the mini-environment apparatus 13•3 comprises ahousing 16•2 constituting a mini-environment space 16•1 arranged forundergoing control of the atmosphere, a gas circulating apparatus 16•3for circulating a gas such as cleaning air in the mini-environment space16•1 to control the atmosphere, a discharge apparatus 16•4 collectingand discharging part of air supplied into the mini-environment space16•1, and a pre-aligner 16•5 placed in the mini-environment space 16•1to roughly position the substrate or wafer as an inspection object.

The housing 16•2 has a top wall 16•6, a bottom wall 16•7 and acircumference wall 16•8 surrounding the circumference, and isolates themini-environment space 16•1 from outside. To atmosphere-control themini-environment space 16•1, the gas circulating apparatus 16•3comprises a gas supply unit 16•9 mounted on the top wall 16•6 to clean agas (air in this embodiment) and flow the clean air just downward in alaminar form through one or more gas blowout holes (not shown) in themini-environment space 16•1, a collection duct 16•10 placed on thebottom wall 16•7 to collect air flowed away toward the bottom in themini-environment space 16•1, a conduit 16•11 connecting the collectionduct 16•10 and the gas supply unit 16•9 to return the collected air backto the gas supply unit 16•9, as shown in FIG. 16.

In this embodiment, the gas supply unit 16•9 introduces about 20% of airto be supplied from outside the housing 16•2 and cleaning the air, butthe ratio of the gas introduced from outside can be arbitrarilyselected. The gas supply unit 16•9 comprises an HEPA or ULPA filterhaving a well known structure for producing clean air. The downwardlaminar flow, namely down flow, is principally supplied in such a manneras to flow through the transportation plane by the first transportationunit placed in the mini-environment space 16•1, described later, toprevent deposition of pasty dust occurring from the transportation uniton the wafer. Thus, a blast nozzle of the down flow is not necessarilylocated near the top wall as shown in the figure, but may be at anylocation on the upper side of the transportation plane by thetransportation unit. Furthermore, it is not required to flow the gasthroughout the mini-environment space 16•1.

Furthermore, in some cases, ion air can be used as clean air to ensurecleanness. Furthermore, a sensor for observing the cleanness may beprovided in the mini-environment space 16•1, and the apparatus may beshut down when the cleanness drops.

An entrance 13•15 is formed in an area adjacent to the cassette holder13•2 in the circumference wall 16•8 of the housing 16•2. A shutterapparatus having a well known structure may be provided near theentrance 13•15 to close the entrance 13•15 from the mini-environmentapparatus side. The laminar down flow produced near the wafer may flowat a flow rate of 0.3 to 0.4 m/sec. The gas supply unit 16•9 may beprovided outside the mini-environment space 16•1, instead of beingprovided inside the mini-environment space 16•1.

The discharge apparatus 16•4 comprises a suction duct 16•12 placed inthe lower part of the transportation unit at a location on the lowerside of the wafer transportation plane of the transportation unit, ablower 16•13 placed outside the housing 16•2 and a conduit 16•14connecting the suction duct 16•12 and the blower 16•13. This dischargeapparatus 16•4 suctions a gas flowing downward along the circumferenceof the transportation unit and containing dust that may occur from thetransportation unit with the suction duct 16•12, and discharges the gasto outside the housing 16•2 through the conduit 16•14 and the blower16•13. In this case, the gas may be discharged into a discharge pipe(not shown) placed near the housing 16•2.

The pre-aligner 16•5 placed in the mini-environment space 16•1 opticallyor mechanically detects an orientation flat (flat portion formed on theouter edge of a circular wafer, which is hereinafter referred to asori-fla) formed on the wafer, and one or more V-type cutouts or notchesformed on the outer edge of the wafer to predefine the position of thewafer in the direction of rotation about the axial line O-O withaccuracy within about ±1°. The pre-aligner 16•5 constitutes part of amechanism determining the coordinates of an inspection object, and playsa role to roughly position the inspection object. The pre-aligner 16•5itself may have a well known structure, and thus the structure andoperation thereof are not presented.

Furthermore, although not shown in the figure, a collection duct fordischarge apparatus may be provided also in the lower part of thepre-aligner 16•5 to discharge air containing dust discharged from thepre-aligner 16•5 to outside.

2-1-3) Main Housing

In FIGS. 13 to 15, the main housing 13•4 constituting the workingchamber 13•16 comprises a housing main body 13•17, and the housing mainbody 13•17 is supported by a housing supporting apparatus 13•20 placedon a vibration blocking apparatus or anti-vibration apparatus 13•19placed on a base frame 13•18. The housing supporting apparatus 13•20comprises a flame structure 13•21 assembled in a rectangular form. Thehousing main body 13•17 is fixedly placed on the frame structure 13•21,comprises a bottom wall 13•22 placed on the frame structure, a top wall13•23, and a circumference wall 13•24 connected to the bottom wall 13•22and the top wall 13•23 to surround the circumference, and isolates theworking chamber 13•16 from outside. In this embodiment, the bottom wall13•22 is made of relatively thick steel plate so that the bottom wall13•22 is not deformed by the weight of equipment such as the stageapparatus and the like placed above, but other structure may be adopted.

In this embodiment, the housing main body and the housing supportingapparatus 13•20 are made to have a rigid structure, and theanti-vibration apparatus 13•19 prevents transfer of vibrations to thisrigid structure from a floor on which the base frame 13•18 is placed. Anentrance 14•1 for loading/unloading the wafer is formed on an area ofthe circumference wall 13•24 of the housing main body 13•17 adjacent toa loader housing described later.

Furthermore, the anti-vibration apparatus 13•19 may be an active typehaving a pneumatic spring, magnetic bearing or the like, or may be apassive type having the same. In any case, the apparatus may have a wellknown structure, and therefore the structure and function of theapparatus itself are not described here. The working chamber 13•16 iskept in a vacuum atmosphere by a vacuum apparatus (not shown) having awell known structure. A control apparatus 2 for controlling theoperation of the overall apparatus is placed below the base frame 13•18.The pressure of the main housing is usually at 10⁻⁴ to 10⁻⁶ Pa.

2-1-4) Loader Housing

In FIGS. 13 to 15 and FIG. 17, the loader housing 13•5 comprises ahousing main body 14•4 constituting a first loading chamber 14•2 and asecond loading chamber 14•3. The housing main body 14•4 has a bottomwall 17•1, a top wall 17•2, a circumference wall 17•3 surrounding thecircumference, and a partition wall 14•5 partitioning the first loadingchamber 14•2 and the second loading chamber 14•3, and can isolate boththe loading chambers from outside. The partition wall 14•5 is providedwith an opening or entrance 17•4 to give and take the wafer between theloading chambers. Furthermore, entrances 14•6 and 14•7 are formed inareas of the circumference wall 17•3 adjacent to the mini-environmentapparatus and the main housing.

The housing main body 14•4 of the loader housing 13•5 is placed andsupported on a frame structure 13•21 of the housing supporting apparatus13•20. Thus, transfer of vibrations of the floor to the loader housing13•5 is also prevented. The entrance 14•6 of the loader housing 13•5 ismatched with an entrance 13•25 of the housing 16•2 of themini-environment apparatus 13•3, and there a shutter apparatus 14•8selectively inhibiting communication between the mini-environment space16•1 and the first loading chamber 14•2 is provided.

The shutter apparatus 14•8 has a seal material 13•26 surrounding theperiphery of entrances 13•25 and 14•6 and fixed in close contact with aside wall 17•3, a door 13•27 inhibiting passage of air through theentrance in cooperation with the seal material 13•26, and a driveapparatus 13•28 driving the door. Furthermore, the entrance 14•7 of theloader housing 13•5 is matched with the entrance 14•1 of the housingmain body 13•17, and there a shutter apparatus 13•29 selectivelyseal-inhibiting communication between the second loading chamber 14•3and the working chamber 13•16 is provided. The shutter apparatus 13•29has a seal material 13•30 surrounding the periphery of entrances 14•7and 14•1 and fixed in close contact with side walls 17•3 and 13•24, adoor 14•9 inhibiting passage of air through the entrance in cooperationwith the seal material 13•30, and a drive apparatus 13•31 driving thedoor.

Further, an opening formed in the partition wall 14•5 is provided with ashutter apparatus 14•10 selectively seal-inhibiting communicationbetween first and second loading chambers by closing the opening withthe door. The shutter apparatuses 14•8. 13•29 and 414•10 can air-tightlyseal the chambers when they are in a closed state. These shutterapparatuses may be well known shutter apparatuses, and thereforedetailed descriptions of the structures and functions thereof are notpresented.

Furthermore, a method of supporting the housing 16•2 of themini-environment apparatus 13•3 is different from a method of supportingthe loader housing, and to prevent vibrations from the floor from beingtransferred through the mini-environment apparatus 13•3 to the loaderhousing 13•5 and the main housing 13•4, a cushion material forprevention of vibrations may be so situated as to air-tightly surroundthe periphery of the entrance between the housing 16•2 and the loaderhousing 13•5.

In the first loading chamber 14•2 is provided a wafer rack 14•11supporting a plurality of wafers (two wafers in this embodiment) in ahorizontal state with the plurality of wafers spaced vertically. Asshown in FIG. 18(A) and FIG. 18(B), the wafer rack 14•11 has poles 18•2mutually spaced and fixed upright at four corners of the rectangularsubstrate 18•1, two-stage support portions 18•3 and 18•4 are formed oneach pole 18•2, and the periphery of the wafer W is borne on the supportportion to hold the wafer. The leading ends of the arms of first andsecond transportation units described later are brought close to thewafer from between adjacent poles to hold the wafer by the arms.

Loading chambers 14•2 and 14•3 can be atmosphere-controlled to be in ahigh vacuum state (degree of vacuum is 10⁻⁴ to 10⁻⁶ Pa) by a vacuumpumping apparatus (not shown) having a well known structure including avacuum pump (not shown). In this case, the first loading chamber 14•2 iskept in low vacuum atmosphere as a low vacuum chamber, and the secondloading chamber 14•3 is kept in a high vacuum atmosphere as a highvacuum chamber, thus making it possible to effectively preventcontamination of the wafer. By employing this structure, the wafer whichis housed in the loading chamber and is to be inspected for defects nextcan be conveyed into the working chamber without delay. By employingthis loading chamber, together with the principle of a multi-beamelectron apparatus described later, the throughput of defect inspectioncan be improved, and the degree of vacuum of the periphery of anelectron source required to be stored under high vacuum conditions canbe kept at as high as possible.

First and second loading chambers 14•2 and 14•3 are each connected to anevacuation pipe and a vent pipe for inert gas (e.g. dry pure nitrogen)(not shown). Consequently, the atmospheric pressure state in eachloading chamber is achieved with inert gas ventilation (introducing aninert gas to prevent deposition on the surface of gases such as oxygengas other than the inert gas). The apparatus itself for inert gasventilation may have a well known structure, and therefore detaileddescriptions thereof are not presented.

Furthermore, in the inspection apparatus of the present invention usingan electron beam, it is important that such a material as, typically,lantern hexaboride (L_(a)B₆) used for an electron source of anelectro-optical system described later is prevented as much as possiblefrom contacting oxygen and the like in order to prolong the life of theelectron source, when the material is heated to such a high temperaturethat thermal electrons are emitted. This can be more reliablyaccomplished by performing the atmosphere control described above in thepre-stage where the wafer is loaded into the working chamber in whichthe electro-optical system is placed.

2-1-5) Loader

The loader 13•7 comprises a robot-type first transportation unit 16•14placed in the housing 16•2 of the mini-environment apparatus 13•3, and arobot-type second transportation unit 14•12 placed in the second loadingchamber 14•3.

The first transportation unit 16•14 has a multi-nodular arm 16•16capable of rotating about an axial line O₁-O₁ with respect to a driveunit 16•15. The multi-nodular arm may have any structure, but in thisembodiment, it has mutually rotatably attached three parts.

One pan of the arm 16•16 of the first transportation unit 16•14, namelya first part closest to the drive unit 16•15 is attached to a shaft16•17 capable of rotating by a drive mechanism (not shown) having a wellknown structure, provided in the drive unit 16•15. The arm 16•16 canrotate about an axial line O₁-O₁ by the shaft 16•17, and can expand andcontract in the radial direction with respect to the axial line O₁-O₁ asa whole by relative rotation among parts. A holding apparatus 14•13holding the wafer such as a mechanical chuck or electrostatic chuckhaving a well known structure is provided at the leading end of a thirdpart remotest from the shaft 16•17 of the arm 16•16. The drive unit16•15 can be moved vertically by a lift mechanism 16•18 having a wellknown structure.

In this first transportation unit 16•14, the arm 16•16 extends in adirection M1 or M2 of one of two cassettes held in the cassette holder,and a wafer housed in the cassette is placed on the arm or held by achuck (not shown) mounted on the arm at the end to take out the wafer.Thereafter, the arm contracts (into a state shown in FIG. 14), rotatesto a position in which the arm can extend in a direction M3 of thepre-aligner 16•5, and stops at the position. Then, the arm extends againand places the wafer held by the arm on the pre-aligner 16•5. The armreceives the wafer from the pre-aligner 16•5 in the opposite manner,then further rotates and stops at a position in which the arm can extendtoward the second loading chamber 14•2 (in direction M4), and places thewafer on a wafer seat in the second loading chamber 14•2. Furthermore,if the wafer is mechanically held, the wafer is held at its periphery(range of about 5 mm from the edge). This is because a device (circuitwiring) is formed on the entire wafer except for the periphery, andholding this area may cause destruction and failure of the device.

The second transportation unit 14•12 has a structure essentiallyidentical to that of the first transportation unit, and the onlydifferent point is that transportation of the wafer is carried outbetween the wafer rack and the holding surface of the stage apparatus,and detailed descriptions thereof are not presented.

In the loader 13•7 described above, first and second transportationunits 16•14 and 14•12 convey the wafer from the cassette held in thecassette holder onto the stage apparatus 13•6 placed in the workingclamber 13•16 and transport the wafer in the opposite manner in almost ahorizontal state, and the arm of the transportation unit movesvertically only when the wafer is taken from and inserted into thecassette, the wafer is placed onto and taken from the wafer rack, andthe wafer is placed onto and taken from the stage apparatus. Thus, largewafer, for example, wafer having a diameter of 300 mm can be movedsmoothly.

Since the stage has a mechanism applying a backward bias to the wafer,the arm is made to have a potential identical or close to that of thestage or a floating potential when the arm is placing the wafer onto thestage or taking the wafer from the stage, whereby a trouble such as adischarge due to potential short is avoided.

2-1-6) Stage Apparatus

The stage apparatus 13•16 comprises a fixed table 13•32 placed on thebottom wall 13•22 of the main housing 13•4, a Y table 13•33 moving inthe Y direction (direction perpendicular to the sheet plane in FIG. 1)on the fixed table, an X table 13•34 moving in the X direction (lateraldirection in FIG. 1) on the Y table, a rotation table 13•35 capable ofrotating on the X table, and a holder 13•36 placed on the rotation table13•35. The wafer is held on a wafer holding surface 14•14 of the holder13•36 in a releasable manner. The holder 13•36 may have a well knownstructure capable of holding in a releasable manner the wafermechanically or in an electrostatic chuck mode. The stage apparatus 13•6uses a servo motor, and encoder and various kinds of sensors (not shown)to operate the plurality of tables described above, whereby the waferheld by the holder on the holding surface 14•14 can be positioned in theX direction, Y direction and Z direction (vertical direction in FIG. 13)with respect to an electron beam emitted from the electro-opticalapparatus, and in the direction of rotation about an axial line verticalto the wafer supporting surface (θ direction) with high accuracy.

Furthermore, for positioning in the Z direction, for example, theposition of the holding surface on the holder may be fine-adjusted inthe Z direction. In this case, a reference position of the holdingsurface is detected by a position measurement apparatus (laserinterference distance measuring apparatus using the principle of theinterferometer) using a laser having a very small diameter, and theposition is controlled by a feedback circuit (not shown), and/or thenotch of the wafer or the position of the oriental-flat is measured todetect a plane position or rotation position of the wafer with respectto the electron beam, and a rotation table is rotated by a steppingmotor or the like capable of performing control at a very small angle tocontrol the position.

For preventing occurrence of dust in the working chamber whereverpossible, servo motors 14•15 and 14•16 and encoders 14•17 and 14•18 forstage apparatus are placed outside the main housing 13•4. Furthermore,the stage apparatus 13•6 may have a well known structure, which is usedin, for example, a stepper, and therefore detailed descriptions of thestructure and operation are not presented. Furthermore, the laserinterference distance measuring apparatus described above may have awell known structure, and therefore detailed descriptions of thestructure and operation are not presented.

An obtained signal can be normalized by previously inputting therotational position and X and Y positions of the wafer with respect tothe electron beam to a signal detection system or image processingsystem described later. Further, a wafer chuck mechanism provided in theholder gives a voltage for chucking the wafer to an electrode of anelectrostatic chick, and holds three points (preferably equally spacedalong the circumference) on the outer edge of the wafer to performpositioning. The wafer chuck mechanism comprises two fixed positioningpins, and one pressing clamp pin. The clamp pin can realize automaticchucking and automatic releasing, and comprises a conduction area forapplication of a voltage.

Furthermore, in this embodiment, the table moving in the lateraldirection is the X table, and the table moving in the vertical directionis the Y table in FIG. 14, but the table moving in the lateral directionmay be the Y table, and the table moving in the vertical direction maybe the X table in this figure.

2-1-7) Wafer Chucking Mechanism

2-1-7-1) Basic Structure of Electrostatic Chuck

For matching the focus of the electro-optical system with the samplesurface correctly and quickly, irregularities on the sample surface orwafer surface are preferably as small as possible. Thus, the wafer isadsorbed to the surface of an electrostatic chuck fabricated with highflatness (preferably flatness of 5 μm or less).

Electrode structures of the electrostatic chuck include a unipole typeand a dipole type. The unipole type is a process in which conduction ispreviously established on the wafer, and a high voltage (generally aboutseveral tens to hundreds V) is applied to between the wafer and oneelectrostatic chuck electrode to adsorb the wafer, while in the dipoletype, it is not necessary to force the wafer into conduction, and thewafer can be adsorbed simply by applying positive and negative voltagesto two electrostatic chucks, respectively. Generally, however, to obtainstable adsorption conditions, two electrodes should be formed into anintricate shape like comb teeth, and thus the shape of the electrodebecomes complicated.

On the other hand, for inspection of the sample, a predetermined voltage(retarding voltage) should be applied to the wafer in order to obtainconditions for image forming for the electro-optical system or ensurethe state of the sample surface that can be easily observed withelectrons. It is necessary that this retarding voltage should be appliedto the wafer, and that the electrostatic chuck should be the unipoletype described above to stabilize the potential of the wafer surface.(However, as described later, the electrostatic chuck should be made tofunction as a dipole type until conduction with the wafer is establishedwith a conduction needle. Thus, the electrostatic chuck has a structurecapable of switching between the unipole type and the dipole type).

Thus, it is required to mechanically contact the wafer to force thewafer into conduction. However, the need for prevention of contaminationof the wafer has intensified, and it is required to avoid mechanicalcontact with the wafer, and there are cases where contact with the edgeof the wafer is not acceptable. In this case, conduction must beestablished on the back face of the wafer.

On the back face of the wafer, a silicon oxide film is usually formed,and it is impossible to establish conduction in this state. Thus,needles are made to contact the back face of the wafer at two or morelocations, and a voltage is applied to between the needles, whereby theoxide film can be locally destructed to establish conduction withsilicon as a wafer base material. The voltage applied to the needles isa DC voltage or AC voltage of several hundreds V. Furthermore, thematerial of the needle should be nonmagnetic, and haveabrasion-resistance and a high melting point, and tungsten or the likecan be considered as such a material. Furthermore, to impart durabilityor prevent contamination of the wafer, it is effective to coat thesurface with TiN or diamond. Furthermore, to ensure that conduction withthe wafer has been established, it is effective to apply a voltage tobetween the needles to measure a current.

It is the chucking mechanism shown in FIG. 19 that has been fabricatedin view of the background described above. The electrostatic chuck isprovided with electrodes 19•1 and 19•2 that desirably have an intricateshape like comb teeth to adsorb the wafer W with stability, three pusherpins 19•3 for giving and taking the wafer, and two or more conductionneedles 19•4 for applying a voltage to the wafer. Furthermore, acorrection ring 19•5 and a wafer dropping mechanism 19•6 are placedaround the electrostatic chuck.

The pusher pin 19•3 already protrudes from the electrostatic chucksurface when the wafer W is conveyed by a robot hand, and when the waferW is placed on the pusher pin 19•3 by the operation of the robot hand,the pusher pin 19•3 slowly descends and places the wafer W onto theelectrostatic chuck. When the wafer is taken from the electrostaticchuck, the opposite operation is made to pass the wafer W to the robothand. The surface material of the pusher pin 19•3 should be selected soas to eliminate the possibility that the wafer position is shifted, andthat the wafer is contaminated, silicon rubber, fluorine rubber,ceramics such as SiC or alumina, a resin such as Teflon or polyamide, orthe like is desirably used.

There are several methods for the drive mechanism of the pusher pin19•3. One is a method of placing a nonmagnetic actuator in the lowerpart of the electrostatic chuck. This may include a method of directlylinear-driving the pusher pin by an ultrasonic linear motor, and amethod of linear-driving the pusher pin by a combination of a rotationalultrasonic motor and a ball screw or rack & pinion gear. In this method,the pusher mechanism can be compactly arranged on a table of an XY stageon which the electrostatic chuck is mounted, the number of wirings ofthe actuator, limit sensor and the like considerably increases. Thewiring extends from the table making XY motions to a sample chamber(main chamber or main housing), but is bent with the motion of thestage, and therefore it should be placed with a large flexure R, andthus takes up a large space. Furthermore, the wiring may become aparticle source, and should be replaced periodically, and therefore anecessary minimum number of wirings should be used.

Thus, as a different method, at external drive force is supplied. Whenthe stage moves to a position at which the wafer W is attached/detached,a shaft protruding into a vacuum atmosphere through a bellow is drivenby an air cylinder provided outside a chamber to press a shaft of apusher drive mechanism provided in the lower part of the electrostaticchuck. The shaft is connected to a rack pinion or link mechanism in thepusher drive mechanism, and the reciprocating motion of the shaft isassociated with the vertical motion of the pusher pin. When the wafer Wis given and taken with the robot hand, the shaft is pushed into thevacuum atmosphere with the air cylinder with the speed adjusted at anappropriate level by a controller, whereby the pusher pin 19•3 is causedto rise.

Furthermore, the external source for driving the shaft is not limited tothe air cylinder, but may be a combination of the servo motor and therack pinion or ball screw. Furthermore, a rotating shaft can be used asthe external drive source. In this case, the rotating shaft operates viaa vacuum seal mechanism such as a magnetic fluid seal, and the pusherdrive mechanism includes a mechanism converting rotation into a linearmotion.

The correction ring 19•5 has an action of keeping uniform an electricfield distribution at end portion of the wafer, and a potentialessentially the same as that of the wafer is applied to the correctionring 19•5. However, to eliminate influences of a very small gap betweenthe wafer and the correction ring and a very small difference in surfaceheight between the wafer and the correction ring, a potential slightlydifferent from that of the end portion of the wafer may be applied. Thecorrection ring has a width of about 10 to 30 mm in the radial directionof the wafer, and a nonmagnetic and conductive material, for exampletitanium, phosphor bronze, aluminum coated with TiN or TiC may be usedfor the correction ring.

The conduction needles 19•4 is supported on a spring 19•7, and islightly pressed against the back face of the wafer with a spring forcewhen the wafer is placed on the electrostatic chuck. In this state,electric conduction with the wafer W is established by applying avoltage as described above.

An electrostatic chuck main body is comprised of nonmagnetic planeelectrodes 19•1 and 19•2 made of tungsten or the like, and a dielectricbody formed thereon. For the material of the dielectric body, alumina,aluminum nitride, polyimide or the like may be used. Generally, ceramicssuch as alumina is a complete isolator having a specific volumeresistance of about 10¹⁴ Ωcm, and therefore causes no charge transferwithin the material, and a coulonbic force acts as absorption force. Onthe other hand, by slightly adjusting a ceramic composition, thespecific volume resistance can be reduced to about 10¹⁰ Ωcm, wherebycharge transfer occurs within the material, and thus so called aJohnson-Rahbek force acts stronger than the coulonbic force acts as awafer absorption force. As the absorption force increases, the appliedvoltage can be reduced accordingly, a larger margin for insulationdestruction can be provided, and a stable absorption force can easily beobtained. Furthermore, by processing the surface of the electrostaticchuck into, for example, a dimple shape, particles may fall to a valleyarea of the dimple even if particles and the like are deposited on thesurface of electrostatic chuck surface, thus making it possible toexpect an effect of reducing the possibility that the flatness of thewafer is affected.

From the above, a practical electrostatic chuck is such that aluminumnitride or alumina ceramics adjusted to have a specific volumeresistance of about 10¹⁰ Ωcm is used as a material, irregularities ofdimple shape or the like are formed on the surface, and the flatness ofthe surface formed by a set of the convexes is about 5 μm.

2-1-7-2) Chucking Mechanism for 200/300 Bridge Tool

The apparatus is required to inspect two types of 200 mm wafer and 300mm wafer without mechanical modification. In this case, theelectrostatic chuck should chuck two types of wafer having differentsizes, and a correction ring matching the size of the wafer should beplaced on the periphery of the wafer. FIGS. 19(A), 19(B) and 20 show astructure therefor.

FIG. 19 shows the wafer W of 300 mm placed on the electrostatic chuck.The correction ring 19•1 having an inner diameter (gap of about 0.5 mm)slightly larger than the size of the wafer W is positioned in such amanner as to be interlocked with a metallic ring part on the outer edgeof the electrostatic chuck. The correction ring 19•1 are provided withwafer dropping mechanisms 19•2 at three locations. The wafer droppingmechanism 19•2 is driven by a vertical drive mechanism associated withthe drive mechanism of the pusher pin 19•3, and is supported rotatablyabout a rotating shaft provided in the correction ring 19•1.

When the water W is received from the robot hand, the pusher pin drivemechanism operates to push the pusher pin 19•3 upward. In appropriatetiming therewith, the wafer dropping mechanism 19•2 provided in thecorrection ring 19•1 rotates under a drive force as shown in FIG. 19(B).Then, the wafer dropping mechanism 19•2 forms a taper plane guiding thewafer W to the center of the electrostatic chuck. Then, the wafer W isplaced on the pusher pin 19•3 pushed upward, and thereafter the pusherpin 19•3 was made to descend. By appropriately adjusting action timingof the drive force for the wafer dropping mechanism 19•2 together withthe descending of the pusher pin 19•3, the wafer W has its positioncorrected by the taper plane of the dropping mechanism 19•2 and placedon the electrostatic chuck so that the center of the wafer W almostmatches the center of the electrostatic chuck.

It is desired that a low frictional material such as Teflon, preferablya conductive low frictional material (e.g. conductive Teflon, conductivediamond like carbon, TIB coating) is formed on the taper plane of thedropping mechanism 19•2. Furthermore, symbols A, B, C, D and E in thefigure denote terminals (described later) for applying a voltage, andreference numeral 19•4 denotes a wafer conducting needle for detectingthat the wafer W is placed on the electrostatic chuck, which is pushedupward by a spring 19•5.

FIG. 20 shows the wafer W of 200 mm placed on the same electrostaticchuck. The surface of the electrostatic chuck is exposed because thediameter of the wafer is smaller than that of the electrostatic chuck,and therefore a correction ring 20•1 having a size so large that theelectrostatic chuck is completely covered. The positioning of thecorrection ring 20•1 is performed in the same manner as in the case ofthe correction ring for the 300 mm wafer.

A step is provided on the inner edge of the correction ring 20•1, andthe correction ring 20•1 is fitted in a ring groove 20•2 on theelectrostatic chuck side. This is a structure for covering the surfaceof the electrostatic chuck with a conductor (correction ring 20•1) sothat the surface of the electrostatic chuck is not seen through a gapbetween the inner edge of the correction ring 20•1 and the outer edge ofthe wafer W when the 200 mm wafer is placed. This is because if thesurface of the electrostatic chuck is exposed, the surface of theelectrostatic chuck is electrically charged to disturb the potential ofthe sample surface when an electron beam is applied.

Replacement of the correction ring 20•11 is performed by providing acorrection ring replacement space at a predetermined position in avacuum chamber, and conveying therefrom a correction ring having anecessary size by a robot and attaching the correction ring to theelectrostatic chuck (inserting the correction ring into an interlockedpart).

The correction ring for the 200 mm wafer is provided with the waferdropping mechanism 20•2 as in the case of the correction ring for the300 mm wafer. A recess is formed on the electrostatic chuck side so asnot to interfere with the wafer dropping mechanism 20•2. The method ofplacing the wafer on the electrostatic chuck is identical to that forthe 300 mm wafer. Furthermore, symbols A, B, C, D and E denote terminalsfor applying a voltage, reference numeral 20•3 denotes a push pinsimilar to the push pin 19•3, and reference numeral 20•4 denotes a waferconducting needle similar to the wafer conducting needle 19•4.

FIGS. 20-1(A) and 20-1(B) schematically show the configuration of theelectrostatic chuck capable of coping with both types of 300 mm waferand 200 mm, in which FIG. 20-1(A) shows the 300 mm wafer placed on theelectrostatic chuck, and FIG. 20-1 (B) shows the 200 mm wafer placed onthe electrostatic chuck. As apparent from FIG. 20-1(A), theelectrostatic chuck has a width large enough to place the 300 mm waferthereon, and as shown in FIG. 21-2(B), the central area of theelectrostatic chuck has a width large enough to place the 200 mm waferthereon, and a groove 20•6 in which the inner ridge of the correctionring 20•1 is to be fitted is provided in such a manner as to surroundthe wafer. Furthermore, symbols A, B, C, D and E denote terminals forapplying a voltage.

In the case of the electrostatic chuck shown in FIGS. 20-1(A) and20-1(B), whether the water is placed on the electrostatic chuck, whetherthe wafer is correctly placed on the electrostatic chuck whether thecorrection ring exists, and so on are optically detected. For example,by placing an optical sensor above the electrostatic chuck, anddetecting an optical path length when light emitted from the opticalsensor is reflected by the wafer and returned back to the opticalsensor, whether the wafer is placed horizontally or slantingly can bedetected. Furthermore, existence/nonexistence of the correction ring canbe detected by providing a light transmitter slantingly irradiating anappropriate point in a space where the correction ring should be placed,and a light receiver receiving reflected light from the correction ring.Further, by providing a combination of the light transmitter slantinglyirradiating the appropriate point in the space where the correction ringfor the 200 mm wafer should be placed and the light receiver receivingreflected light from the correction ring, and a combination of the lighttransmitter slantingly irradiating the appropriate point in the spacewhere the correction ring for the 300 mm wafer should be placed and thelight receiver receiving reflected light from the correction ring, anddetecting which light receiver receives reflected light, which of thecorrection ring for the 200 mm wafer and the correction ring for the 300mm wafer is placed on the electrostatic chuck can be detected.

2-1-7-3) Wafer Chucking Procedure

The wafer chucking mechanism having the structure described above chucksthe wafer according to the following procedure.

(1) A correction ring matching the size of the wafer is carried by arobot and placed on the electrostatic chuck.

(2) The wafer is placed on the electrostatic chuck by transportation ofthe wafer by a robot hand and vertical motions of the pusher pin.

(3) A voltage is applied to the electrostatic chuck in a dipole type(positive and negative voltages are applied to terminals C and D) toadsorb the wafer.

(4) A predetermined voltage is applied to a conducting needle todestruct an insulation film (oxide film) on the back face of the wafer.

(5) A current between terminals A and B is measured to check whetherconduction with the wafer is established.

(6) A transition of the electrostatic chuck to a unipole type adsorptionis made (terminals A and B are set to GRD, and the same voltage isapplied to terminals C and D).

(7) The voltage of the terminal A, (B) is decreased while keeping adifference in potential between the terminal A, (B) and the terminal C,(D), and a predetermined retarding voltage is applied to the wafer.

2-1-8) Apparatus Configuration for 200/300 Bridge Tool

The configuration for achieving an apparatus capable of inspecting the200 mm wafer and the 300 mm wafer without mechanical modification isshown in FIG. 21 and FIG. 22. Aspects in which the apparatus isdifferent from the apparatus dedicated for the 200 mm wafer or theapparatus dedicated for the 300 mm wafer will be described below.

At an installation site 21•1 of the wafer cassette that is replaced forspecifications of the 200/300 mm wafer, FOUP, SMIF, the open cassetteand the like, the wafer cassette appropriate to the wafer size and thetype of wafer cassette determined depending on user specifications canbe placed. An atmosphere transportation robot 21•2 has a hand capable ofcoping with different wafer sizes, i.e. a plurality of wafer droppingportions are provided in conformity with the wafer sizes, and the waferis placed on the hand at a location matching the wafer size. Theatmosphere transportation robot 21•2 sends the wafer from theinstallation site 21•1 to a pre-aligner 21•3, regulates the orientationof the wafer, then takes the wafer from the pre-aligner 21•3, and sendsthe wafer into a load lock chamber 21•4.

A wafer rack in the load lock chamber 21•4 has a similar structure, aplurality of dropping portions matching wafer sizes are formed in awafer support portion of the water rack, the height of the robot hand isadjusted so that the wafer placed on the hand of the atmospheretransportation robot 21•2 is placed in the dropping portion matching thesize of the wafer, the wafer is inserted into the wafer rack, and thenthe robot hand descends to place the wafer in a predetermined droppingportion of the wafer support portion.

The wafer placed on the wafer rack in the load lock chamber 21•4 is thentaken from a load lock chamber 21•3 by a vacuum transportation robot21•6 installed in a transfer chamber 21•5, and conveyed onto a stage21•8 in the sample chamber 21•7. The hand of the vacuum transportationrobot 21•6 has a plurality of dropping portions matching wafer sizes asin the case of the atmosphere transportation robot 21•2. The waferplaced in a predetermined dropping portion of the robot hand is placedon the electrostatic chuck having previously mounted a correction ring21•9 matching the wafer size in the stage 21•8, and fixedly adsorbed bythe electrostatic chuck. The correction ring 21•9 is placed on acorrection ring rack 21•10 provided in the transportation chamber 21•5.Then, the vacuum transportation robot 21•6 takes the correction ring21•9 matching the wafer size from the correction ring rack 21•10, andconveys the correction ring 21•9 onto the electrostatic chuck, fits thecorrection ring 21•9 in a positioning interlocked part formed on theouter edge of the electrostatic chuck, and then places the wafer on theelectrostatic chuck.

When the correction ring is replaced, the opposite operation is carriedout. That is, the correction ring 21•9 is removed from the electrostaticchuck by the robot 21•6, the correction ring is returned back to thecorrection ring rack 21•10 in the transfer chamber 21•5, and thecorrection ring matching the size of the wafer to be inspected next isconveyed from the correction ring rack 21•10 to the electrostatic chuck.

In the inspection apparatus shown in FIG. 21, the pre-aligner 21•3 islocated close to the load lock chamber 22•4, and therefore the wafer iseasily returned back to the pre-aligner for realignment if alignment ofthe wafer is not adequate enough to place the correction ring in theload lock chamber, thus bringing about an advantage that time loss inthe step can be reduced.

FIG. 22 shows an example of changing a site where the correction ring isplaced, in which the correction ring rack 21•10 is omitted. In the loadlock chamber 22•1, the wafer rack and the correction ring rack areformed in a layered form, and they can be placed in an elevator to movevertically. First, to place the correction ring matching the size of thewafer to be inspected next on the electrostatic chuck, the vacuumtransportation robot 21•6 moves the elevator of the load lock chamber22•1 to a position where the correction ring can be taken out. When, thecorrection ring is placed on the electrostatic chuck by the vacuumtransportation robot 21•6, then the elevator is manipulated so that thewafer to be inspected can be transferred, and the wafer is taken fromthe wafer rack by the vacuum transportation robot 21•6, and then placedon the electrostatic chuck. This configuration requires an elevator inthe load lock chamber 22•1, but can downsize the vacuum transportationchamber 21•5, and is thus effective in reducing a foot print of theapparatus.

Furthermore, a sensor detecting whether or not the wafer exists on theelectrostatic chuck is desirably placed at a position such that thesensor can cope with any of different wafer sizes, but if it isimpossible, a plurality of sensors working in the same manner may beplaced for each wafer size.

The inspection apparatus described with respect to FIG. 21 employs aprocedure in which the correction ring is placed on the electrostaticchuck, and the wafer is positioned so that the wafer fits the innerdiameter of the correction ring. Then, the inspection apparatus shown inFIG. 22 employs a procedure in which the correction ring is mounted onthe wafer in the load lock chamber 22•1, and the wafer with thecorrection ring mounted thereon is conveyed together with the correctionring into the sample chamber 21•7, and mounted on the electrostaticchuck on the stage. Mechanisms for realizing the procedure include anelevator mechanism for vertically moving an elevator to pass the waferfrom the atmosphere transportation robot to the vacuum transportationrobot, shown in FIGS. 22-1 and 22-2. A procedure of conveying the waferusing this mechanism will be described below.

As shown in FIG. 22-1 (A), the elevator mechanism provided in the loadlock chamber has multistage (two-stage in the figure) correction ringsupports base so situated as to be movable in the vertical direction. Anupper-stage correction ring support base 22•2 and lower-stage correctionring support base 22•3 are fixed on a first base 22•5 rising/descendingwith rotation of a first motor 22•4, whereby the first base 22•5 andupper and lower correction ring support bases 22•2 and 22•3 move upwardor downward with rotation of the first motor 22•4.

The correction ring 22•6 having an inner diameter matching the size ofthe wafer is placed on each correction ring support base. For thecorrection ring 22•6, two types having different inner diameters, i.e.the type for the 200 mm wafer and the type for the 300 mm wafer, areprepared, and they have the same outer diameter. In this way, by usingcorrection rings having the same outer diameter, mutual compatibility isprovided, thus making it possible to place the correction ring in theload lock chamber in an arbitrary combination of the correction ring forthe 200 mm wafer and the correction ring for the 300 mm wafer. That is,for a line in which 200 mm wafers and 300 mm wafers flow in a mixedform, inspection can be performed flexibly for either type of wafer withthe upper stage set for the 300 mm wafer and the lower stage set for the200 mm wafer. Furthermore, for a line in which wafers of the same sizeflow, wafers in upper and lower stages can be inspected alternately withupper and lower stages set for the 200 mm or 300 mm wafer, thus makingit possible to improve the throughput.

A second motor 22•7 is placed on the first base 22•5, and a second base22•8 is vertically movably attached to the second motor 22•7. An upperwafer support base 22•9 and a lower wafer support base 22•10 are fixedon the second base 22•8. Consequently, when the second motor 22•7rotates, the second base 22•8 and upper and lower wafer support bases22•9 and 22•10 move upward or downward in one united body.

Then, as shown in FIG. 22-1(A), the wafer W is placed on the hand of theatmosphere transportation robot 21•2 and loaded into the load lockchamber 22•1, and then as shown in FIG. 22-1(B), the second motor 22•7is rotated in a first direction to move the wafer support bases 22•9 and22•10 upward to place the wafer W on the upper-stage wafer support base22•9. In this way, the wafer W is moved from the atmospheretransportation robot 21•1 to the wafer support base 22•9. Thereafter, asshown in FIG. 22-1(C), the atmosphere transportation robot 21•2 is movedbackward, and when the backward movement of the atmospheretransportation robot 21•2 is completed, the second motor 22•7 is rotatedin a direction opposite to the first direction to move the wafer supportbases 22•9 and 22•10 downward as shown in FIG. 22-1(D). In this way, thewafer W is placed on the correction ring 22•6 in the upper-stage.

Then, as shown in FIG. 22-1(E), the hand of the vacuum transportationrobot 21•6 is introduced into the load lock chamber 22•1 and stopped atbelow the correction ring 22•6. In this state, the first motor 22•4 isrotated, and as shown in FIG. 22-1(F), the first base 22•5, the upperand lower correction ring support bases 22•2, 22•3, the second motor22•7, and the upper and lower wafer support bases 22•9 and 22•10 aremoved downward, whereby the correction ring 21•6 placed on theupper-stage wafer support base 22•9, and the wafer W can be placed onthe hand of the vacuum transportation robot 21•6 and loaded into thesample chamber 21•7.

The operation of returning the wafer inspected in the sample chamber21•7 back to the load lock chamber 21•4 is carried out in a procedureopposite to the procedure described above, and the wafer loaded onto thewafer support base together with the correction ring by the vacuumtransportation robot is transferred to the correction ring support base,then to the wafer support base, and finally placed on the atmospheretransportation robot. Furthermore, in FIGS. 22-1 and 22-2, the operationof giving and taking the wafer in the upper stage is described, but thesame operation can be carried out in the lower stage by adjusting theheights of the hands of the atmosphere transportation robot 21•2 and thevacuum transportation robot 21•6. In this way, by appropriately changingthe heights of the hands of the atmosphere transportation robot 21•2 andthe vacuum transportation robot 21•6, the wafer that has not beeninspected yet can be loaded into the sample chamber from one stage, andthen the inspected wafer can be unloaded to the other stage from thesample chamber in an alternate manner.

2-2) Method for Transportation of Wafer

Transportation of the wafer from the cassette 13•12 supported by thecassette holder 13•2 to the stage apparatus 13•6 placed in the workingchamber 13•16 will now be described in order (see FIGS. 14 to 16).

If the cassette is manually set as described previously, the cassetteholder 13•2 having a structure suitable for this application is used,while if the cassette is automatically set, the cassette holder 13•2having a structure suitable for this application is used. In thisembodiment, when the cassette 13•12 is set on the lift table 13•13 ofthe cassette holder 13•2, the lift table 13•13 is made to descend by thelift mechanism 13•14, and the cassette 13•12 is matched with theentrance 13•15. When the cassette is matched with the entrance 13•15, acover (not shown) provided in the cassette is opened, a cylindricalcover is placed between the cassette and the entrance 13•15 of themini-environment apparatus 13•3 to isolate the inside of the cassetteand the inside of the mini-environment space from the outside. Thestructures thereof are well known, and therefore detailed descriptionsof the structures and functions are not presented. Furthermore, if ashutter apparatus for opening and closing the entrance 13•15 is providedon the mini-environment apparatus 13•3 side, the shutter apparatusoperates to open the entrance 13•15.

On the other hand, the arm 16•16 of the first transportation unit 16•14is stopped while being oriented in any of the direction M1 and thedirection M2 (oriented in the direction M1 in this description), andwhen the entrance 13•15 is opened, the arm extends to receive one ofwafers housed in the housing at the leading end. Furthermore, adjustmentof the position of the arm and the wafer to be taken from the cassettein the vertical direction is performed with the vertical movement of thedrive unit 16•15 of the first transportation unit 16•14 and the arm16•16 in this embodiment, but it may be performed with the verticalmovement of the lift table of the cassette holder or with both thevertical movements.

When the reception of the wafer by the arm 16•16 is completed, the armcontracts and operates the shutter apparatus to close the entrance (ifthe shutter apparatus exists), and then the arm 16•16 rotates about theaxial line O₁-O₁ so that it can extend in the direction M3. Then, thearm extends to place the wafer placed on the leading end or held by thechuck on the pre-aligner 16•5, and the orientation of the wafer in therotational direction (orientation about the central axial lineperpendicular to the wafer plane) is positioned within a predeterminedrange by the pre-aligner 16•5. When the positioning is completed, thetransportation unit 16•14 receives the wafer from the pre-aligner 16•5at the leading end of the arm, and then makes the arm contract so thatthe arm can be extend in the direction M4. Then, the door 13•27 of theshutter apparatus 14•8 moves to open entrances 13•25 and 13•37, and thearm 16•16 extends to place the wafer on the upper stage or lower stageside of the wafer rack 14•11 in the first loading chamber 14•2.Furthermore, before the shutter apparatus 14•8 is opened to pass thewafer to the wafer rack 14•11 as describe previously, the opening 17•4formed in the partition wall 14•5 is air-tightly closed with the door14•19 of the shutter apparatus 14•10.

In the process of transportation of the wafer by the firsttransportation unit 16•14, clean air flows (as a down flow) in laminarform from the gas supply unit 16•9 provided on the housing of themini-environment apparatus 13•3 to prevent deposition of dust on thewafer during transportation. Part of air around the transportation unit(about 20% of air supplied from the supply unit, which is mainlycontaminated air, in this embodiment) is suctioned from the suction duct16•12 of the discharge apparatus 16•4 and discharged to the outside ofthe housing. Remaining air is collected via the collection duct 16•10provided on the bottom of the housing and returned back to the gassupply unit 16•9.

When the wafer is placed in the wafer rack 14•11 in the first loadingchamber 14•2 of the loader housing 13•5 by the first transportation unit16•14, the shutter apparatus 14•8 is closed to seal the loading chamber14•2. Then, an inert gas is filled in the first loading chamber 14•2 topurge air, and then the inert gas is discharged to create a vacuumatmosphere in the loading chamber 14•2. The vacuum atmosphere of thefirst loading chamber 14•2 may have a low degree of vacuum. When asatisfactory degree of vacuum is achieved in the loading chamber 14•2,the shutter apparatus 14•10 operates to open the shutter 14•5 of theentrance 17•4 closed with the door 14•19, the arm 14•20 of the secondtransportation unit 14•12 extends to receive one wafer from the waferseat 14•11 by a holding apparatus at the leading end (placing the waferon the leading end, or holding the wafer by a chuck mounted at theleading end). When the reception of the wafer is completed, the armcontracts, and the shutter apparatus 14•10 operates again to close theentrance 17•4 with the door 14•19.

Furthermore, before the shutter apparatus 14•10 is opened, the arm 14•20takes a posture in which the arm 14•20 can extend in the direction N1 ofthe wafer rack 14•11. Furthermore, entrances 14•7 and 14•1 are closedwith the door 14•9 of the shutter apparatus 13•29 before the shutterapparatus 14•10 is opened as described previously, communication betweenthe second loading chamber 14•3 and the working chamber 13•16 isinhibited in an air-tight state, and the second loading chamber 14•3 isevacuated.

When the shutter apparatus 14•10 closes the entrance 17•4, the secondloading chamber 14•3 is evacuated again to have a degree of vacuumhigher than that of the first loading chamber 14•2. In the meantime, thearm of the second transportation unit 16•14 is rotated to a position inwhich it can extend toward the stage apparatus 13•6 in the workingchamber 13•16. On the other hand, in the stage apparatus 13•6 in theworking chamber 13•16, the Y table 13•33 moves upward to a position inwhich the center line X₀-X₀ of the X table 13•34 almost matches the Xaxis line X₁-X₁ passing through the rotation axis line O₂-O₂ of thesecond transportation unit 14•12 in FIG. 14, and the X table 13•34 movesto a position close to the leftmost position in FIG. 14, and waits inthis state. When the degree of vacuum of the second loading chamber 14•3is approximately the same as that of the working chamber 13•16, the door14•9 of the shutter apparatus 13•29 moves to open the entrances 14•7 and14•1, and the arm extends so that the leading end of the arm holding thewafer approaches the stage apparatus 13•6 in the working chamber 13•16.The wafer is placed on the holding surface 14•14 of the stage apparatus13•6. The placement of the wafer is completed, the arm contracts, andthe shutter apparatus 13•29 closes the entrances 14•7 and 14•1.

Since the stage has a mechanism applying a backward bias potential(retarding potential) to the wafer, the arm is made to have a potentialidentical or close to that of the stage, or the arm is made to have afloating potential when the arm goes to place or take the wafer, wherebya trouble such as a discharge due to a short of the potential isavoided. Furthermore, as another embodiment the bias potential to thewafer may be kept off when the wafer is conveyed onto the stageapparatus.

If the bias potential is controlled, the potential is kept off until thewafer is conveyed to the stage, and the bias potential may be turned onand applied after the wafer is conveyed to the stage. For timing ofapplying the bias potential, tact time is preset, and the bias potentialmay be applied based on the tact time, or placement of the wafer on thestage is detected with a sensor, and the bias potential may be appliedusing the detection signal as a trigger. Furthermore, the closing of theentrances 14•7 and 14•1 by the shutter apparatus 13•29 is detected, andthe bias potential may be applied using the detection signal as atrigger. Further, if the electrostatic chuck is used, adsorption by theelectrostatic chuck is confirmed, and this may be used as trigger toapply the bias potential.

The operation of conveying the wafer in the cassette 13•12 onto thestage apparatus has been described above, and for returning the wafer,which has been placed on the stage apparatus 13•6 and processed, fromthe stage apparatus 13•6 into the cassette 13•12, the operation oppositeto that described above is made. Furthermore, since a plurality ofwafers are placed or the wafer rack 11•11, the wafer can be conveyedbetween the cassette and the wafer rack 14•11 in the firsttransportation unit 16•14 while the wafer is conveyed between the waferrack 14•11 and the stage apparatus 13•16 in the second transportationunit 14•12, thus making it possible to carry out inspection processingefficiently.

Specifically, if a processed wafer A and an unprocessed wafer B exist inthe wafer rack 14•11, the unprocessed wafer B is first moved to thestage 13•6. In the mean time, the processed wafer A is moved from thewafer rack to the cassette 13•12 by the arm, and an unprocessed wafer Cis taken from the cassette 13•12 by the arm, positioned by thepre-aligner 16•5, and then moved to the wafer rack 14•11 of the loadingchamber 14•2.

In this way, in the wafer rack 14•11, the processed wafer A can bereplaced with the unprocessed wafer C while the wafer B is processed.Furthermore, depending on the use of the apparatus for performinginspection and evaluation, a plurality of stage apparatuses 13•6 areplaced side by side, and the wafer is moved to each apparatus from onewafer rack 14•11, whereby a plurality of wafers can be subjected to thesame processing.

FIG. 23 shows an alteration example of a method of supporting the mainhousing 13•4. In the alteration example shown in FIG. 23, a housingsupporting apparatus 23•1 is composed of a thick and rectangular steelplate 23•2, and the housing main body 23•3 is placed on the steel plate.Thus, a bottom wall 23•4 of the housing main body 23•1 is thinner thanthe bottom wall of the embodiment described previously. In an alterationexample shown in FIG. 24, a housing main body 24•3 and a loader housing24•4 are supported in a suspended state by a frame structure 24•2 of ahousing supporting apparatus 24•1.

The lower ends of a plurality of longitudinal frames 24•5 fixed to theframe structure 24•2 are fixed at four corners of a bottom wall 24•6 ofthe housing main body 24•3, and a circumference wall and a top wall aresupported by the bottom wall. An anti-vibration apparatus 24•7 is placedbetween the frame structure 24•2 and a base frame 24•8. Furthermore, theloader housing 24•4 is suspended by a suspending member 24•9 fixed tothe frame structure 24•2. In the alteration example of the housing mainbody 24•3 shown in this figure, the total weight at the center ofgravity of the main housing and various kinds of devices providedtherein can be reduced owing to the support in a suspended manner. Inthe method for supporting the main housing and the loader housingincluding the above alteration example, vibrations from the floor arenot transferred to the main housing and the loader housing.

In another alteration example (not shown), only the housing main body ofthe main housing is supported from below by the housing supportingapparatus, and the loader housing can be placed on the floor in the samemanner as the case of the adjacent mini-environment apparatus 13•3.Furthermore, in still another alteration example, only the housing mainbody of the main housing 13•4 is supported by the frame structure in asuspended manner, and the loader housing can be placed on the floor inthe same manner as the case of the adjacent mini-environment apparatus.

According to the embodiments described above, the following effects canbe exhibited.

(1) The entire configuration of a projection electron microscope typeinspection apparatus using an electron beam can be obtained, and aninspection object can be processed with high throughput.

(2) Clean air is flowed through the inspection object in themini-environment space to prevent deposition of dust, and a sensor forobserving the cleanness is provided, whereby the inspection object canbe inspected while monitoring dust in the space.

(3) Since the loading chamber and the working chamber are integrallysupported via the vibration preventing apparatus, the inspection objectcan be supplied to the stage apparatus and inspected without beinginfluenced by the external environment.

2-3) Electro-Optical System

2-3-1) Overview

The electro-optical system 13•8 comprises an electro-optical systemcomprising a primary electro-optical system (hereinafter referred tosimply as primary optical system) 25•1 schematically shown in FIG. 25-1,provided in a column 13•38 fixed to the housing main body 13•17, and asecondary electro-optical system (hereinafter referred to simply assecondary optical system) 25•2, and a detection system 25•3. The primaryoptical system 25•1 is an optical system irradiating an electron beam tothe surface of the wafer W as an inspection object, and comprises anelectron gun 25•4 emitting an electron beam, a lens system 25•5comprised of an electrostatic lens converging a primary electron beamemitted from the electron gun 25•4, a Wien filter or E×B separator 25•6,and an objective (or cathode) lens system 25•7, and they are placed inorder with the electron gun 25•4 situated at the uppermost position asshown in FIG. 25-1. A lens constituting the objective lens system 25•7of this embodiment is a retarding electric field objective lens. In thisembodiment, the optical axis of the primary electron beam emitted fromthe electron gun 25•4 is slanted with respect to the axis (perpendicularto the surface of the wafer) of irradiation beam irradiated to the waferW as an inspection object. An electrode 25•8 is placed between theobjective lens system 25•7 and the wafer W as an inspection object. Theelectrode 25•8 is axially symmetric with respect to the axis ofirradiation beam of the primary electron beam, and voltage-controlled bya power supply 25•9.

The secondary optical system 25•2 comprises a lens system 25•10comprised of an electrostatic lens penetrable to secondary electronsseparated from the primary optical system by the E×B type deflector25•6. This lens system 25•10 functions as a magnifying lens magnifying asecondary electron image.

The detection system 25•3 comprises a detector 25•11 and an imageprocessing unit 25•12 placed on an imaging surface of the lens system25•10.

The direction of incident of the primary beam is usually the E directionof the E×B filter (direction opposite to the electric field), and thisdirection is identical to the integration direction of anintegration-type line sensor (TDI: time delay integration). Theintegration direction of the TDI may be different from the direction ofthe first beam.

The electron beam optical system column comprises the followingcomponents.

(1) Column Magnetic Shield

A nickel alloy such as permalloy or a magnetic material such as iron issuitably used for a member constituting the column, whereby an effect ofinhibiting the influence of magnetic disturbance can be expected.

(2) Detector Rotation Mechanism

To match the scan axis direction of the stage with the scan direction ofthe detector, the column 13•38 has in its upper part a detector rotationmechanism eliminating a deviation in the scan direction caused byassembly of apparatus by allowing the detector 25•11 such as the TDI torotate at ±several degrees about the optical axis while keeping theinside of the column 13•38 under vacuum. In this mechanism, about 5 to40 seconds are required for rotational resolution and rotationalposition reproducibility. This arises from the requirement that adeviation between the scan direction of the stage and the scan directionof the detector should be about 1/10 of one pixel during the scanning ofan image of one flame. According to the detector rotation mechanism, anangular error between the direction of movement of the stage and theintegration direction of the TDI can be adjusted to be 10 mrad or less,preferably 1 mrad or less, more preferably 0.2 mrad or less.

One example of the configuration of the detector rotation mechanism willbe described below using FIGS. 25-3 to 25-5. FIG. 25-3 shows the overallconfiguration of the detector rotation mechanism provided in the upperpart of the column 13•38, FIG. 25-4 is a schematic diagram of amechanism for rotating an upper column, and FIG. 25-5 shows a mechanismfor sealing the upper column and a lower column.

In FIG. 25-3, the upper end of the column 13•38 is comprised of an uppercolumn 25•20 having the detector 25•11 attached thereto, and a lowercolumn 25•21 fixed to the main housing 13•4. The upper column 25•20 issupported on the lower column 25•21 via a bearing 25•22 and can rotateabout the optical axis of the secondary optical system, and a sealportion 25•23 is provided between the upper column 25•20 and the lowercolumn 25•21 to keep the inside of the column 13•38 under vacuum.Specifically, the seal portion 25•23 is placed between the lower end ofthe upper column 25•20 and the upper end of the lower column 25•21, aflange portion 25•24 is provided at the upper end of the lower column25•21 in such a manner as to surround the upper column 25•20, and thehearing 25•22 is placed between the flange portion 25•24 and the sideface of the upper column 25•20.

Bearing clamps 25•25 and 25•26 for clamping the bearing 25•22 arescrewed to the upper column 25•20 and the lower column 25•21,respectively. Further, to rotate the upper column 25•20 with respect tothe lower column 25•21, a drive mechanism shown in FIG. 25-4 isprovided. That is, a raised portion 25•27 is provided in part of thebearing clamp 25•26 provided at the upper end of the flange portion25•24, while an actuator 25•29 is fixed on a mounting member (bracket)25•28 protruding from the upper column 25•20. A shaft 25•30 of theactuator 25•29 contacts the raised portion 25•27, and a precompressionspring 25•31 given a force for attraction toward the raised portion25•27 is provided between the flange portion 25•24 and the mountingmember (bracket) 25•28 having the actuator 29•29 fixed thereon.Consequently, by activating the actuator 25•29 to change the length ofthe shaft 25•30 protruding from the actuator 25•29, the upper column25•20 can be rotated at a desired angle in a desired direction withrespect to the lower column 25•21.

For the rotation accuracy described above, the movement resolution ofthe actuator 25•29 is desirably 5 to 10 μm. Furthermore, the actuator25•29 may be a piezo actuator or actuator motor-driving a micrometer.Furthermore, a sensor capable of measuring a relative distance betweenthe bracket 25•28 for fixing the actuator 25•29 and the raised portion25•27 is desirably mounted to measure a rotational position of thedetector 25•11. For the sensor, a linear scale, potentiometer, laserdisplacement meter, deformation gage or the like may be used.

The seal portion 25•23 is placed so that a very small gap 25•32 (FIG.25-5) is formed between the upper end face of the lower column 25•21 andthe lower end face of the upper column 25•20 as shown in FIG. 25-5 tokeep the inside of the column 13•38 under vacuum. The seal portion 25•23comprises a partition ring 25•33 solidly fixed at the center, and twoelastic seals 25•34 and 25•35, and springs 25•36 and 25•37 for ensuringthe contact pressure of the seal surface to improve a sealingperformance are provided between lip portions of the elastic seals 25•34and 25•35, respectively. An air exhaust port 25-39 communicating with anair exhaust channel 25•38 formed in the lower column 25•21 is providedat the center of the partition ring 25•33. The elastic seals 25•34 and25•35 are preferably made of a material having a very small frictionalcoefficient and being excellent in slidability and for example,Omni-seal manufactured by Huron Co., Ltd. (USA) may be used.

In this way, the elastic seal is doubly placed, and a space 25•40between the elastic seals is evacuated, whereby even if the upper column25•20 rotates to cause a very small leak to occur in the elastic seal25•35 on the atmosphere side, the leaked air is exhausted through theair exhaust channel 25•38, and thus the pressure of the space 25•40 doesnot significantly increase. Therefore, no leak occurs from the elasticseal 25•34 into the column, so that the vacuum in the column is neverdegraded. The space 25•40 may be continuously evacuated, but it is alsopossible to evacuate the space 25•40 only when the detector rotationmechanism is activated. This is because the leak is more likely to occurwhen the detector is rotated, and sufficient sealing is ensured with thepressure of contact between the elastic seals 25•34 and 25•35 and thelower end of the upper column 25•20 when the detector is not rotated.

It is important that the pressure of contact between the elastic seals25•34 and 25•35 and the upper and lower surfaces is appropriately set,and this can be realized by adjusting the size of the gap 25•32. Theadjustment of the gap 25•32 can be performed by inserting a shim 25•41between the bearing 25•22 and the upper end face of the lower column25•21. By inserting the shim 25•41 in this position, the height of thebearing 25•22 with respect to the lower column 25•21 can be changed. Onthe other hand, for the upper column 25•20, the bearing 25•22 is heldbetween clamps 25•25 and 25•26, and therefore the bearing 25•22 movesvertically together with the upper column 25•20, and the gap 25•32between the upper column 25•20 and the lower column 25•21 changes by thethickness of the shim 25•41.

Furthermore, depending on specifications of the column, a sufficientperformance is obtained even if only a single seal is provided insteadof providing double seals and the space between seals is not evacuatedas shown in FIG. 25-5. However, double seals are more reliable, andallow a high vacuum to be easily produced. Furthermore, the springs25•36 and 25•37 are provided in the elastic seals 25•34 and 25•35 in theabove description, but if the elastic seals 25•34 and 25•25 aresufficiently pressed against the upper and lower surfaces with apressure difference between the vacuum and the atmosphere, or theelastic seals 25•34 and 25•35 themselves have sufficient repulsiveforces, the springs 25•36 and 25•37 may be omitted.

To match the direction of the detector with the direction of the stagewith the rotation mechanism having the configuration described above,the detector 25•11 is rotated in a very small amount, the scan imagingof the detector 25•11 is carried out on each such an occasion, and theangle of the detector 25•11 is matched with the angle when the mostsharp image is obtained. A specific process thereof will be describedbelow.

In the rotatable range of the detector rotation mechanism, the detector25•11 is rotated at a very small angle to carry out the scan imaging ofthe detector 25•11, and the obtained image is subjected to imageprocessing, whereby a numerical value allowing evaluation of imagequality such as a contrast is determined. This process is repeated todetermine a relation between the rotational position of the detector25•11 and the image quality, and a rotational position for best imagequality is determined. Then, the detector 25•11 is rotated to theposition to complete the operation of positioning the detector 25•11.

An allowable value for a positional deviation between the stage and thedetector 25•11 depends on the requirement that a deviation between thescan direction of the stage and the scan direction of the detectorshould be about 1/10 of one pixel during the scanning of an image of oneframe in the detector 25•11. Thus, an allowable angular deviation whenpixels are arranged in 500 stages along the scan direction is about 40seconds.

To set the angular deviation between the stage and the detector to 40seconds or less, a method in which the relation between the position ofthe detector and the image quality described above is expressed as anumerical value by a method such as multinominal approximation, and aposition of the detector 25•11 for best image quality is determined, ora method in which the detector 25•11 is first roughly rotated to form animage, an approximate relation between the position of the detector andthe image quality is determined, a range of a position of the detectorfor best image quality is identified, the detector is again rotated in avery small amount in this range to carry out the same operation, and aposition of the detector for best image quality is accurately determinedcan be used. To prevent occurrence of an angular deviation aftermatching the angles of the stage and the detector in this way, it iseffective to provide a lock mechanism. For example, a planar part isplaced between the bearing clamps 25•25 and 25•26, and this platy partand the bearing claims 25•25 and 25•26 are fixed together with a bolt.

(3) NA Movement Mechanism

The NA is held by a mechanism capable of moving several centimetersalong the optical axis or m a direction orthogenal to the light axis,and allows an adjustment to be made so that the NA is situated at anoptically optimum position according to a change in magnifying power. Aplurality of NAs can be desirably mounted on a NA holding unit, and byadding such a mechanism, the NA can be replaced while keeping the insideof the column under vacuum when the NA is degraded or a change intransmittance is desired.

Furthermore, a heater unit is desirably installed in the NA holding unitto provide an effect of inhibiting degradation of the NA by keeping theNA at a high temperature. Furthermore, it is effective to install apiping unit for a reactive gas, so that the NA can be cleaned whilekeeping the inside of the column under vacuum.

(4) Isolation Valve

A valve allowing the inside of the column to be partitioned into aplurality of spaces is desirably installed in the column. Specifically,it is effective to install the valve so that the space of an MCP unit orelectron gun unit can be separated from the space of the stage unit.Such a configuration enables maintenance of the periphery of the stageand the like to be carried out while keeping the MCP unit and theelectron gun unit under vacuum. Furthermore, conversely, maintenance ofthe MCP unit and the electron gun unit can be carried out while keepingthe stage unit and the like under vacuum.

(5) Shield Barrel

The optical axis is preferably surrounded by a grounded cylindricalmember, and by providing such a configuration, an effect of inhibitingthe influence of electric external disturbance can be expected.

(6) Orifice Before MCP

An orifice-like or slim cylindrical member is placed between a series ofelectro-optical system and the MCP unit reduces, and by providing aconfiguration such that a conductance of a path extending through aspace between the electro-optical system and MCP unit, the pressure ofthe MCP unit can be easily kept at about ⅕, preferably about 1/10, morepreferably about 1/100 of the pressure of the electro-optical system.

(7) Integration of Electrodes and Enhancement of Accuracy

Parts required to be installed on an electro-optically concentric axiswith accuracy of several μm or smaller are desirably assembled by amethod such as inter-member combination processing or cooling fit.

(8) Optical Microscope

An optical microscope is provided to compare a sample image under lowmagnifying power and an image seen under light with an electron beamimage. The magnification is about 1/10 to 1/5000, preferably about 1/20to 1/1000, more preferably about 1/20 to 1/100 of that of electron teamimage. An image of light from the sample surface can be detected by atwo-dimensional solid imaging device (CCD), and displayed on a CRT.Furthermore, it can be stored in a memory.

(9) Coaxial Ion Pump

By installing a non-vibration type vacuum pumping system such as an ionpump rotation-symmetrically around an optical axis near the electron gununit and the MCP unit, an effect of keeping such a place under highvacuum while offsetting the influences of charged particles and magneticfields by the pumping system itself can be expected. This is because areduction in conductance of piping is alleviated when the ion pump isconnected to the electron gun unit and the like to evacuate the same.

Specific embodiments will be described below.

(1) Embodiment 1

The embodiment is one example of inspection apparatus mainly comprisedof a vacuum chamber, a vacuum pumping system, a primary optical system,a secondary optical system, a detector, an image processing unit and acomputer for control. One example thereof is shown in FIG. 26.

A primary optical system 26•1 for illuminating an electron beam to asample, and a secondary optical system 26•2 for guiding electronsemitted from the sample surface, for example secondary electrons,reflection electrons, back-scattered electrons, to the detector areprovided. The secondary optical system is a projection electronmicroscope type optical system. A beam separator 26•3 of E×B is used forseparating the primary system and the secondary system. Furthermore, animage signal of an electron detected by a detector 26•4 is an opticalsignal or/and an electric signal, and processed by an image processingunit 26•5. Furthermore, at this time, if the number of electronsentering the detector is 200 or less per one pixel equivalent area, animage can be formed satisfactorily. Of course, the image can besatisfactorily formed if the number of electrons is 200 or greater perone pixel area.

An electron gun 26•6 as a component of the primary optical system usesLaB₆ as a heat filament (cathode), and derives electrons from a cathodewith a Wenelt and draw electrode 26•7. Then, a beam is converged to anaperture 26•9 with a two-stage A lens (Einzell lens) 26•8 to form acrossover. Then, the beam passes through a two-stage aligner 26•10, anaperture 26•11, a three-stage quadrupole lens 26•12 and a three-stagealigner 26•13, enters a beam separator, is deflected in the direction ofthe sample surface, passes through an aperture 26•14 and a P lens(objective lens) 16•16 of the secondary system, and is applied to thesample surface almost vertically.

The aligner (deflector) 26•10 making the beam to pass through a beamarea highly uniform in crossover and having a high luminance by theaperture 26•9, and specifying an angle of a beam incident to thequadrupole lens by the aperture 26•11 is used for adjustment to causethe beam enter at the center of the optical axes of the aperture 26•11and the quadrupole lens 26•12. The quadrupole lens 26•12 is used fordeformation of the beam shape by changing paths of the bean in twodirections, for example X and Y directions. For example, in the shape ofthe sample irradiation bean, a change in ratio of shapes of circular,elliptic, rectangular and rectangular/elliptic shapes in x and ydirections can be achieved (see FIG. 27). After passing through thequadrupole lens, the beam is adjusted to pass through an aperture 26•15and the center of the P lens (objective lens) 26•16 by the aligner26•14, and enters the sample surface. At this time, the shape of theirradiation beam can be symmetrically formed for at least one of twoaxes. The beam may have an asymmetric shape. Energy of the beam appliedto the sample surface is finally determined by a difference in voltagebetween the cathode and the sample surface. For example, when thevoltage of the cathode is 5.0 kV and the voltage of the sample surfaceis 4 kV, energy of the irradiation beam is 1 key (see FIG. 26).

In this case, the voltage error is ±10 V, and the energy error is ±20eV. Furthermore, if secondary electrons are used as detection electrons,the sample is negatively charged, and secondary electrons are emittedfrom the sample in this state, made to form an image under magnificationby the secondary optical system, and guided to the detection system whenthe beam irradiation energy of 1.5 keV±10 eV to 5 keV±10 eV is used. Ifthe irradiation energy is 50±10 eV to 1500 eV±10 eV, the sample surfaceis positively charged, and emitted secondary electrons are guided to thedetection system. When the sample is positively charged, the operationcan be carried out with a relatively low damage, but the sample is moreeasily influenced by charge-up or unevenness in surface potential due tothe charge-up. In the negative charge operation, an image can be easilyobtained with stability, and the influence of charge-up or distortion ofthe image due to unevenness in surface potential by the charge-up can bereduced compared to the case of positive charge.

Furthermore, at the location of the aperture 26•15, the operation may becarried out with positions of crossovers of the secondary system and theprimary system deviated from each other. For example, the crossover ofsecondary electrons is formed on the center of the secondary systemoptical axis for the secondary system, and the crossover of the primarysystem is formed at a position deviated by 50 to 500 μm from the centerof the optical axis of the secondary system (may be either X or Y).Consequently, two crossovers of the primary system and the secondarysystem never overlap each other in the aperture 26•15, and the currentdensity can be alleviated, thus making it possible to inhibit expansionof blurs due to the space charge effect when the amount of beam currentis large. This is effective when the current density of the primarysystem irradiation beam is greater than 1×10⁻³ A/cm², for example. Forany lower current density, there is no influence even if the centers ofoptical axes are identical.

For electrons emitted from the sample surface, at least one type ofsecondary electrons, reflection electrons and back scattered electronsare used. The levels of energy emitted from the sample surface are 0 to10 eV, 1000 eV±10 eV and 10 to 1000 eV, respectively, for incident beamenergy of 1000 eV±10 eV, for example. Furthermore, electrons passingthrough a thin film or a bored sample (e.g. slancil mask) are used. Inthis case, for the former thin sample, the incident energy is reduced bythe amount equivalent to the thickness of the sample, and for the boredsample, the incident energy remains unchanged.

A focused ion beam (FIB) may be used instead of the electron beam. A Gaion source of a liquid metal is generally used as the FIB source, butother liquid metal ion source using a metal that is easily liquefied, oran ion source of a different type, for example a duoplasmatron using adischarge may be used.

For the sample, various samples such as a tip of about 10×10 mm, and 2,4, 6, 8 and 12 inch wafers are used. Particularly, it is effective indetection of defects of a wiring pattern having a line width of 100 nmor smaller and a via having a diameter of 100 nm or smaller, andcontaminants, and also convenient for detection of electric defects ofthe pattern and the via. For the sample. Si wafers, semiconductor devicewafers made by processing Si, micromachined wafers, substrates forliquid crystal displays, head-processed wafers for hard disks and thelike are used.

For the secondary system 26•2, an example will be described in which aprojection type optical system to make electrons emitted from thesample, for example secondary electrons, reflection electrons,back-scattered electrons and transmission electrons form an image undermagnification and guide the electrons to the detection system is used.As an example of the lens configuration of a column, the lens isconstituted by a P lens (objective lens) 26•16, the aperture 26•15, thealigner 26•14, the beam separator 26•3, a P lens (intermediate lens)26•17, the aligner 26•18, the aperture 26•19, a P lens (projection lens)26•20, an aligner 26•21, and a micro-channel plate (MCP) unit. Ahermetic quartz glass is placed on an upper flange of the column. Arelay lens and a two-dimensional charge coupled device (2D-CCD) areplaced thereon, and an image formed on a fluorescent screen is formed ona 2D-CCD sensor.

Emitted electrons from the sample surface form a crossover in theaperture 26•15 at the P lens (objective lens) 26•16, and are made toform an image at the center of the beam separator 26•3. The operationunder conditions of forming an image at the center of the beam separatoris effective because the effect of an aberration of a secondary beamoccurring in the beam separator 26•3 can be reduced to a low level. Thisis because for example, the deflection amount/aberration variesdepending on the image height when the beam is made to pass at E×B, andtherefore the aberration suffered by image formation components can bereduced to a minimum due to formation of the image. Since this is alsotrue for the primary system, not only image formation conditions areformed on the sample but also an image formation point is formed nearthe center of the beam separator, whereby the aberration of the primarybeam is reduced, and unevenness of the current density on the sample iseffectively reduced.

To adjust the beam to be situated at the center of the P lens(intermediate lens) 26•17 thereon, the aligner 26•14 is used. To adjustthe beam to be situated at the center of the P lens (projection lens)26•20 in the upstream thereof, the aligner 26•18 is used. To adjust thebeam to be situated at the center of the MCP thereon, the aligner 26•21exists. The magnification of the P lens (objective lens) 26•16 is 1.5×to 3× the magnification of the P lens (intermediate lens) 26•17 is 1.5×to 3×, and the magnification of the P lens (projection lens) 26•20 is30× to 50×. To achieve these magnifications, a voltage appropriate toeach of the magnifications is applied to each lens to make anadjustment. Furthermore, to make a fine adjustment of a focus, adedicated focus correction lens is incorporated in the P lens (objectivelens) system, and focusing is achieved by fine adjustment of the voltageapplied to the electrode. At locations of the aperture 26•15 and theaperture 26•19, the aperture 26•15 can be used to cut noises, and theaperture 26•19 can be used so that it plays a role to determine anaberration/contrast if the crossover is formed in both cases.

For the size, for example, the aperture 26•15 and the aperture 26•19 canbe used at φ30 to φ2000 μm, preferably φ30 to φ1000 μm, more preferablyφ30 to φ500 μm. At this time, if the aberration, the transmittance andthe contrast characteristic are mainly determined with the aperture26•15, the aperture 26•15 is used at, for example, φ30 to φ500 μm, andthe aperture 26•19 is used at φ1000 to φ2000 μm. If the aberration, thetransmittance and the contrast characteristic are mainly determined withthe aperture 26•19, for example, the aperture 26•19 is used at φ30 toφ500 μm, and the aperture 26•15 is used at φ1000 to φ2000 μm.

Furthermore, astigmatic electrodes may be placed above and below the Plens (intermediate lens) 27•17. The electrodes are used to correct anastigmatic aberration occurring due to the beam separator 26•3 and thelike. For example, an astigmatic electrode having an electrodeconfiguration of 4, 6 or 8 poles can be used. For example, differentvoltages may be applied to the eight electrodes to correct theastigmatic aberration and the spherical aberration.

Furthermore, in the lens operation when a reflection electrode image andback-scattered electrons are used, the P lens (projection lens) 26•20 inthe last stage is effective in cutting noises of secondary electrons ifa retarding lens (negative voltage application lens) is used for the Plens. Usually, the amount of secondary electrons is greater than theamount of reflection electrodes by a factor of 10 to 1000, and thereforethe retarding lens is especially effective when image formation isperformed using reflection electrons/back-scattered electrons. Forexample, when a cathode voltage of a primary system electron source is 4kV, a sample potential is 3 kV, the level of reflection electron energyfrom the sample is 1 keV, and when a detector voltage is an installationvoltage, a difference in energy level between the reflection electronand the secondary electron is about 1 keV at the site of a P electrode.At this time, in the negative voltage lens operation of the P lens(projection lens), conditions such that the central voltage allows thereflection electron to pass and cuts off the secondary electron can beused. The conditions can be determined by means of simulation.

For the beam separator 26•3, a separator operating with E×B where theelectrode is orthogonal to the magnetic pole, or only with a magneticfield B is used. As an example, an E×B is comprised of an E electrodeforming an electric field distribution and a magnetic pole having a poleface orthogonal to the E electrode and forming a magnetic flux densitydistribution in a direction orthogonal to the E electrode. For example,when the optical axis of the secondary system is perpendicular to thesample surface, the incident beam of the primary system can be set at 10to 90 degrees with respect to the axis of the secondary system. At thistime, the beam of the primary system is deflected with E×B and canperpendicularly enter the sample surface, and emitted electrons from thesample surface are guided in the direction of the optical axis, i.e. inthe direction perpendicular to the sample surface with E×B. This isachieved by a voltage applied to the E electrode, and a magnetic fluxdensity formed in the B electrode. For example, a voltage of ±2 kV±1 Vis applied to a pair of E electrodes, a magnetic flux densitydistribution is formed in parallel from a pair of B electrodes and forexample, at the center of E×B, a magnetic flux density of 1 to 60 G±1 Gin the direction of the magnetic pole is produced (see FIG. 26).

Furthermore, E×B can also be applied to the inversed deflection relationof the primary system and the secondary system. That is, the incidentbeam source of the primary system is provided just above the sample, thedetector of the secondary system is provided at an angle of 10 to 80degrees with respect to the axis of the primary system, the beam of theprimary system is made to enter the sample without applying a deflectionforce thereto with E×B, and the deflection force is applied to electronsemitted from the sample (beam of secondary system), whereby theelections can be guided to the detector.

In the detector 26•4, signal electrons are introduced into an electronmultiplier tube 28•1 such as an MCP, and amplified electrons are appliedto a fluorescent screen to form a fluorescent image. The fluorescentscreen has a glass plate 28•2 such as quartz glass coated with afluorescent material on one side. The fluorescent image is formed by arelay lens system 28•3 on a two-dimensional CCD 28•4. This relay lenssystem and the CCD are placed on the column. A hermetic glass 28•6 isplaced on an upper flange of the column, the vacuum environment in thecolumn is separated from the external atmospheric environment, thefluorescent image is formed on the CCD with deformation/contrastdegradation being reduced, and the fluorescent image can be efficientlyformed.

An integration-type line image sensor (TDI-CCD) camera can be usedinstead of the CCD. In this case, TDI imaging can be performed while thesample is stage-moved, for example, in the direction of the E electrodeor the direction of the B magnetic pole on the stage. For example, whenthe number of TDI integration stages is 256, one stage has 2048 pixels,the element size is 15×15 μm, and the magnification of the MCP imageformation with respect to the sample surface is 300×, the size of thesample surface may be 30/30 μm for the MCP surface if the line/space is0.1/0.1 μm. When the magnification of the relay lens is 1×, imaging isperformed with the size of two elements being equivalent to 30 μm. Atthis time, electrons emitted from the sample position equivalent to oneelement, i.e. the sample size of 0 05×0.05 μm are integrated duringmovement on the stage equivalent to 256 element stages, and the totalamount of acquired light increases to allow imaging to be performed.This is especially effective when the stage speed is high such as aspeed corresponding to a line rate of 100 kHz to 600 kHz. This isbecause when the line rate is high, the number of acquired electrons perelement, i.e. the intensity of acquired light per element of the TDIsensor decreases, and thus integration can be carried out to enhance thefinal density of acquired light and increase the contrast and S/N. Theline rate is 0.5 kHz to 100 MHz, preferably 1 kHz to 50 MHz, morepreferably 20 kHz to 10 MHz. In correspondence therewith, a video rateis 1 to 120 MHz/tap, preferably 10 to 50 MHz/tap, more preferably 10 to40 MHz/tap. Furthermore, the number of taps is 1 to 520, preferably 4 to256, more preferably 32 to 128 (see FIGS. 28 and 29).

The CCD and the TDI sensor/camera that are used have characteristics oflow noises and high sensitivities. For example, they can be set at 100to 100000 DN/(nJ/cm²) but above all, if they are used at 1000 to 50000DN/(nJ/cm²), the efficiency is improved. Further, if they are used at10000 to 50000 DN/(nJ/cm²), a high quality image can be obtained withgood S/N even when the line rate is high.

Furthermore, when the image is acquired using the CCD or TDI sensor, itcan be used in a state in which a region of the number of pixels thenumber of stages almost matches an area irradiated with the primarybeam, thus improving efficiency and reducing noises. For the noise,electrons from a site of a large image height other than areasmiscellaneously used may reach the detector as noises. To reduce thesenoises, it is effective to reduce beam irradiations at a site other thanan effective field. Image information acquired by the CCD or TDI sensoris converted into an electric signal, and subjected to data processingby an image processor. Through this image processing, image comparisonis carried out on a cell-to-cell, die-to-die, die-to-any die basis, andthus defects can be inspected. For example, pattern defects, particledefects, and potential contrast defects (e.g. electric connectiondefects of wiring and plating) are inspected.

For the stage 26-22, a stage installed with a combination of at leastone of X, Y, Z and θ movement mechanisms is used. In this electron beaminspection apparatus, the following components can be used as thecomponents described above.

Primary System

Electron source: W filament, L_(a)B₆ filament, TFE, FE

Lens: made of metal or ceramic, phosphor bronze as metal, Ti, Al,Einzwell lens, quadrupole lens

Aligner: lenses of 4 poles, 6 poles and 8 poles

Aperture: materials, Mo, Ta, Ti, phosphor bronze

Secondary System

Lens: made of metal or ceramic, phosphor bronze as metal, Ti, Al,ceramic electrode subjected to treatment such as Au plating Einzelllens, quadrupole lens

Aligner: lenses of 4 poles, 6 poles and 8 poles

Aperture: materials, Mo (molybdenum) Ta, Ti, phosphor bronze

Electron Beam Separator

E electrode: made of metal or ceramic, phosphor bronze as metal. Ti, Al,ceramic electrode subjected to treatment such as Au plating

B magnetic pole: permalloy B, permalloy C, etc., material having a highsaturation magnetic flux density and magnetic permeability (e.g. 10³ to10⁷, preferably 10⁴ to 10⁷, more preferably 10⁵ to 10⁷)

Sample

Si wafer, 3 to 5 group compound semiconductor water, crystal substrate,head-processed wafer of hard disk, 2, 4, 6, 8 and 12 inch wafers

Detector

MCP/fluorescent screen/relay lens/CCP

MCP/fluorescent screen/relay lens/TDI

MCP/fluorescent screen/FOP (fiber optic plate)/TDI

Photomultiplier

Multi-photomultiplier

The detector can be used in the combinations described above. The MCPhas a function to amplitude entering electrons, and the electronsexiting therefrom are converted into light by the fluorescent screen. Ifthe amount of entering electrons is so large that they are not requiredto be amplified, the operation can be performed without the MCP.Furthermore, a scintillator can be used instead of the fluorescentscreen. A light signal thereof (or image signal) is transmitted to theTDI or forms an image under a predetermined magnification in the case ofthe relay lens, and under a magnification of 1× (light signal istransmitted in a ratio of 1:1) in the case of the FOP. Thephotomultiplier amplifies a light signal and converts the light signalinto an electric signal, and the multi-photomultiplier has a pluralityof photomultipliers arranged.Image ProcessorThe image processor has functions of image comparison, defect detection,defect classification, image data recording and the like.

In the electron beam inspection apparatus, an irradiation beam shape ofthe primary beam symmetrical with respect to at least one axis of X andY axes can be used. Accordingly, an acquired image can formed with a lowaberration and low deformation on the electron beam entrance surface ofthe detector by the beam having an optical axis at the center.

Furthermore, if the CCD or TDI is used as the detector, a sufficient S/Nratio can be achieved in an area corresponding to one pixel, for examplein an area where the number of entering electrons is 200/pixel orsmaller in formation of one pixel on the MCP, thus making it possible touse the detector for image processing and defect detection. In theprojection type optical system, for example, noise cut and aberrationreduction effects can be achieved by specifying the size of the aperture26•15 or 26•19, and therefore by placing an aperture having a diameterof 30 μm to 1000 μm, for example, an improvement in S/N ratio can beachieved, thus making it possible to acquire an image of high resolutionand high quality in an area of 200 electrons/pixel.

TDI performs integration equivalent to the number of stages for thedirection of movement of the stage. Integration equivalent to 256 stagesis performed in this embodiment, but the number of integration stages isappropriately 114 to 8192, preferably 114 to 4096, more preferably 512to 4096. Even if there is slight unevenness in illuminance of theprimary beam in the direction of integration, and there is unevenness insignal electrons from the sample, the unevenness is equalized due to theeffect of integration, and detected electron information is constant andstable. Thus, in consideration of a direction where unevenness inilluminance of the primary electron beam easily occurs, the direction ofmovement of the stage can be determined so that the direction where theilluminance unevenness easily occurs matches the direction ofintegration of the TDI. The image can be continuously acquired by usingthe TDI, but the CCD may be used to scan the stage in the step andrepeat mode to acquire the image. That is, the operation of stopping thestage at a specific location to acquire an image, then moving the stageto a next location, and stopping the stage there to acquire an image isrepeated. A similar operation can be carried out using the TDI. That is,the still mode of the TDI (pause image acquirement mode, in which thestage is stopped) is used, or an image of a certain area (e.g. 2048pixels×2048 pixels) is acquired by a usual image acquirement process ofthe TDI, and then the stage is moved to a next location (no image isacquired during the movement), where an image is similarly acquired.Thus, in this case, inspection is performed without stopping themovement of the stage.

When the appearance of the sample surface is magnified by electrons toform an image on the detector, an aberration, a blur and the like of thesecondary optical system is desirably within one pixel if the resolutionof the image is limited to about one pixel of the CCD or TDI. Since theaberration and the blur grow if electrons are deflected at E×B, signalelectrons such as secondary electrons, reflection electrons andback-scattered electrons are adjusted to travel in straight lines withno deflection force given thereto in the secondary optical system inthis embodiment. That is, the central axis of the secondary opticalsystem is a straight line passing through the center of the field ofview of the sample, the center of E×B and the center of the detector.

Furthermore, since cases other than the embodiment described above areacceptable as long as no blur occurs in the image of the secondaryoptical system, such cases are included in this invention as a matte ofcourse.

(2) Embodiment 2

When the TDI sensor/camera is used for the detector in the inspectionapparatus similar to the embodiment 1, the image can be acquired morequickly and efficiently if the number of images/stages is 2048 to 4096,the number of taps is 32 to 128, and the sensitivity is 10000 to 40000DN/(nJ/cm²). At this time, the line rate may be 100 to 400 kHz, and thevideo rate may be 10 MHz to 40 MHz. At this time, the operation iscapable of being done when an 8 inch Si wafer, for example LSI devicewafer is used, the resolution is 0.1 μm/pixel, and inspection time perone wafer is ⅛ to 2 hours.

At this time, when the resolution is 0.1 μm/pixel, a contrast of 3 to30% is achieved, and thus image observation and defect detection can besufficiently performed even with a pattern shape of, for example,LS:0.2/0.2 μm in sample observation and defect inspection. A defecthaving a shape other than L/S can be detected by comparison using achange in contrast as long as the defect has a size of one pixel orgreater. A contrast of 5 to 30% is achieved, thus making it possible toperform observation and defect inspection by image processing.Furthermore, for the LSI device wafer, defects of the design rule orsmaller can be detected. Defects equivalent to the half pitch of thewiring width can be detected for the memory, and defects equivalent tothe gate length can be detected for the logic.

When defects are detected using the TDI sensor/camera and an imageprocessing mechanism, the image can be continuously formed to performinspection continuously by the TDI operation. At this time, the sampleis placed on the stage, and continuous operations are similarly carriedout to obtain the image. The speed of the stage is essentiallydetermined by v=f×D, wherein v represents a stage speed, f represents aline frequency and D represents a size corresponding to sensor pixels onthe sample (determined by a projection magnification). For example, whenf is 300 kHz and D is 0.1 μm, v equals 30 mm/s.

FIG. 29 shows an example of a detection system having a configurationdifferent from that of the embodiment 1 shown in FIG. 28. In this case,an MCP 29•2, an FOP 29•3, a TDI sensor/package 29•4, a contact pin 29•5and a field-through flange 29•6 are provided in a column 29•1 undervacuum, and an output of the TDI sensor 29•4 is received by a TDI camera29•7 through the field-through flange 29•6. Furthermore, the FOP 29•3 iscoated with a fluorescent material to form a fluorescent image byelectrons from the MCP 29•2. The fluorescent image is transmitted to theTDI sensor 29•4 by the FOP 29•3. An image signal of the TDI sensor 29•4is transmitted to the TDI camera 29•7 via the contact pin 29•5 and thefield-through flange 29•6. At this time, use of the FOP 29•3 can reducean optical signal transmission loss. For example, the transmittanceincreases by a factor of about 5 to 20 compared the relay lens. This isespecially effective when the TDI operation is carried out. This isbecause quicker activation is possible due to high intensity of theacquired optical signal, and signal unevenness of a fiber shape isreduced to a negligible level by integration of the TDI. Here, thecontact pin 29•5 for connecting pins of the TDI sensor 29•4 and thefield though flange 29•6 is required. The contact pin 29•5 isconnection-fixed to one side (e.g. pin of field-through) by fit contact,and contacts the pin of the TDI sensor/package with an elastic force ofa spring (not shown).

Consequently, the pin of the field-through flange 29•6 and the pin ofthe TDI sensor/package 294 can be installed with a low pressing force,in a parallel position and at a low impedance. In a high speed operationsensor, a large number of pins are used and for example, more than 100pins are required. If the number of pins is large, the installationpressure (pressing force) increases, and thus the TDI sensor/package29•4 may be broken. Such points have been overcome to make installationpossible.

As shown in FIG. 28, the CCD or TDI is usually installed at theatmosphere side, and the MCP and the fluorescent screen are installedunder vacuum, but by placing the CCD or TDI under vacuum, the relayoptical system such as the FOP can be curtailed, thus making it possibleto improve transmission efficiency.

(3) Embodiment 3

In this embodiment, an EB-CCD or EB-TDI is used for the detector (seeFIG. 30) in the embodiments 1 and 2. The EB is an electron beam, and theEB-CCD or EB-TDI directly inputs the electron beam, and converts it intoan electric signal (not detecting an optical signal).

Use of the EB-TDI sensor/camera can inject electrons directly into animage portion of the sensor, accumulate charges. This means that it isunnecessary to use the fluorescent screen, the relay lens and hermeticglass used in the usual detector. That is, since an electric signal canbe obtained directly from an electron signal without temporarilyconverting an electron signal image into an optical signal image, andthus a loss associated with the conversion can be considerably reduced.That is, image deformation by the fluorescent screen, hermetic glass andthe relay lens system, degradation in contrast, and deleterious effectssuch as variations in magnification can be considerably reduced.Furthermore, due to reduction in the number of components, downsizing,cost-reduction and quick operations can be achieved. Quick operationscan reduce a signal transmission speed loss and an image formation speedloss.

One example of a unit of the EB-TDI is shown in FIG. 30. See theembodiment 1 for the optical system. The surface of a TDI sensor 30•3 isplaced in the upper part of a secondary system column, i.e. on theimage-forming point the upper part of the P lens (projection lens). Theunit is comprised of a TDI sensor/package 30•3, a contact pin 30•4, afield-through 30•5, a TDI camera 30•1, and image processor 30•6 and acontrol PC 30•7. Emitted electrons (any of secondary electrons,reflection electrons and back-scattered electrons) from the samplesurface are made to form an image by the secondary system and enter thesurface of the TDI sensor 30•3. Charges are accumulated in accordancewith the amount of electrons, and an electric signal for image formationis formed by the TDI camera 30•1.

A pin of the sensor package 30•3 and a pin of the field-through flange30•5 are connected together by the contact pin 30•4. In this aspect,this embodiment is similar to the embodiment 2. In this case, since anelectric image signal is converted directly into an electric signal bythe TDI sensor 30•3, components and parts can be curtailed and thetransmission channel can be shortened compared to the detectors of theembodiments 1 and 2. This makes it possible to achieve improvement inS/N due to reduction in noises, speed enhancement, downsizing andcost-reduction.

The EB-TDI 30•1 is used in this embodiment, but the EB-CCD may besimilarly used. Particularly, this configuration is effective if thenumber of required pins is greater than 100 due to a large number ofpixels or to perform high speed operations. A contact pin for connectingthe pin of the field-through and the package is required. The contactpin is constituted by a spring material and a contact plate on one side(e.g. on the package side), and can reduce the contact width. If thereare a large number of contact pins, for example 100 or more contactpins, a pressing force at the time of connection increases, and if thetotal force exceeds 5 kg, a problem of rupture of the package arises.Thus, a contact pin having a pressing force limited to 50 to 10 g/pin byadjustment of a spring force is used.

Furthermore, the number of incident electrons is insufficient when theEB-CCD or EB-TDI is used, an MCP being an electron multiplier tube canbe used. Furthermore, for the number of images/stages, the number ofstages, the number of taps, the line rate and the video rate, conditionssimilar to those of the embodiments 1 and 2 may be used. The sensitivitycan be 0.1 to 10000 DN/electron.

(4) Embodiment 4

In the inspection apparatus similar to the embodiments 1, 2 and 3, aprimary system 31•1 has the same configuration, but a secondary system31•2 has a different configuration as shown in FIG. 31. To achieve ahigher resolution, a two-stage P lens (objective lens) 31•3, a two-stageP lens (intermediate lens) 31•5, and a two-stage P lens (projectionlens) 31•8 are used. Further, the P lens (intermediate lens) is notablya zoom lens. Consequently, a projection-type beam optical system havinga higher resolution and a larger visual field size compared toconventional systems can be achieved, and an image of any magnificationcan be acquired in the zoom range.

2-3-2) Details of Configuration

An electron gun, a primary optical system, a secondary optical system,an E×B unit, a detector and a power supply of an electro-optical systemshown in FIGS. 25-1 to 31 will be described in detail below.

2-3-2-1) Electron Gun (Electron Beam Source)

A thermal electron beam source is used as an electron beam source. Anelectron emission (emitter) material is L_(a)B₆. Any other material canbe used as long as the material has a high melting point (low vaporpressure at high temperature) and a small work function. A materialhaving the leading end formed into a conic shape, or a material having aconic shape with the leading end cut off is used. The diameter of theleading end of the truncated cone is about 100 μm. For other types, anelectric field emission type electron beam source or thermal electricfield emission type is used, but when a relatively wide area (e.g.100×25 to 400×100 μm²) is irradiated with a large amount of current(about 1 μA) as in the present invention, a thermal electron sourceusing L_(a)B₆ is most suitable. Furthermore, in the SEM system, athermal electric field electron beam source (TFE type) and a short keytype are generally used. The thermal electron beam source is a system inwhich the electron emission material is heated to emit electrons, andthe thermal electric field emission electron beam source is a system inwhich a high electric field is applied to the electron emission materialto emit electrons, and an electron beam emission portion is heated tostabilize the emission of electrons. In this system, extraction ofelectron beams under efficient conditions called shot key conditions canbe performed by selecting the temperature and the electric fieldintensity and recently, this system has been often used.

2-3-2-2) Primary Optical System

A part forming an electron beam applied from an electron gun, andirradiating an electron beam having a two-dimensional cross section suchas a rectangular, circular or elliptic cross section or a linearelectron beam onto the wafer surface is called a primary electro-opticalsystem. By controlling lens conditions of the primary electro-opticalsystem, the beam size and the current density are controlled. By an E×Bfilter (Wien filter) at a primary/secondary electro-optical systemconnection portion, a primary electron beam is made to enter the waferat a right angle (±5°, preferably ±3°, more preferably ±1°).

Thermal electrons emitted from a L_(a)B₆ cathode are made to form animage on a gun diaphragm as a crossover image by a Wenelt, triple anodelens, double anode, or single anode. An electron beam having the angleof incidence to the lens modified by an illumination visual fielddiaphragm is made to form an image on an NA diaphragm in a form ofrotational asymmetry by controlling a primary system electrostatic lens,and then applied to the wafer surface. The rear stage of a quadrupolelens of the primary system is comprised of a three-stage quadrupole (QL)and a one-stage aperture aberration correcting electrode. The quadrupolelens has a constraint of strict alignment accuracy, but notably has astrong convergence action compared to the rotational symmetry lens, andis capable of correcting an aperture aberration corresponding to aspherical aberration of the rotational symmetry lens by applying anappropriate voltage to the aperture aberration correcting electrode.Consequently, a uniform plane beam can be applied to a predeterminedarea. Furthermore, the electron beam can be scanned by a deflector.

The shape and area of the irradiation electron beam on the samplesurface includes the shape and area of an imaging area of the TDI-CCD onthe sample, and it is desirable that the illuminance in the electronbeam irradiation area is uniform, and illuminance unevenness is 10% orless, preferably 5% or less, more preferably 3% or less.

The shape and area of the TDI-CCD in this embodiment is equivalent to apixel number of 2048×512, with the pixel size being 16 μm×16 μm, andtherefore its overall shape is a rectangle of about 32.8 mm×3.2 mm. Whenthe magnification of the secondary optical system is 160×, theirradiation area on the sample surface is 1/160 of 32.8 mm×8.2 mm, andis therefore a rectangle of 205 μm×51.2 μm.

Thus, the electron beam irradiation area in this case is desirably arectangle including a rectangle of 205 μm×51.2 μm, but it may be arectangle having round corners, ellipse, circle or the like as shown inFIG. 27-1 as long as its shape and area meets the above conditions. Whenthe magnification of the secondary optical system is 320×, theirradiation area is 1/320 of 32.8 mm×8.2 mm, which is equivalent to arectangle of 102.4 μm×25.6 μm, thus being ¼ of the irradiation area withthe magnification of 160×.

In this way, in the present invention, a beam with a relatively largearea including imaging areas of the TDI-CCD as a detector is applied tothe sample, the imaging areas on the sample correspond to pixels of theTDI-CCD, respectively, and electrons emitted from these imaging areas onthe sample are made to form an image on the TDI-CCD at a time to performdetection.

The irradiation shape of the electron beam may be linear, and may bescanned to ensure an irradiation are the same as that of a plane beam. Alinear beam 27•1 refers to a beam having a shape in which thelength-to-width ratio is 10:1 or greater as shown in FIGS. 27-2(1-1) and27(1-2), it is not limited to a rectangle but may be an ellipse.Furthermore, the linear beam 27•1 may have interrupted at some midpointas shown in FIG. 27-2(2). The scanning of the beam reduces the timeperiod over which the beam is continuously applied to the same locationof the sample, and thus has an advantage that the influence of charge upon the sample is reduced.

FIGS. 27-2(3) and 27-2(4) show a relation between a multi-pixel imagingarea 27•3 of the TDI-CCD and the linear beam 27•1 on an inspectionsubject 27•2. Among them, in FIG. 27-2(3), the linear beam 27•1 isplaced at almost a right angle (e.g. 90°±3°, preferably 90°±1°) withrespect to an integration direction 27•4 of the TDI-CCD or a directionof movement 27•5 of the XY stage, and a direction of scan 27•6 of thebeam is identical to the integration direction 28•4 or the direction ofmovement 27•5 of the XY stage (e.g. 0°±1°), preferably 0°±1 minute, morepreferably 0°±1 second).

FIG. 27-2(4) shows another example, in which the linear beam 27•1 isalmost parallel to the integration direction 27•4 of the TDI-CCD or thedirection of movement of the XY stage (e.g. 90°±1°, preferably 90°±1minute, more preferably 90°±3 seconds).

2-3-2-3) Secondary Optical System

A two-dimensional secondary electron image produced by an electron beamapplied to the wafer is formed at a visual field throttling position byan electrostatic lens equivalent to an objective lens, and magnified andprojected by a lens (PL) in the rear stage. This image formation andprojection optical system is called a secondary electro-optical system.A negative bias voltage (retarding electric field voltage) is applied tothe wafer. The retarding electric field has an effect of retarding theirradiation beam to reduce damage on the sample, and acceleratingsecondary electrons generated from the sample surface with a differencein potential between the objective lens and the wafer to reduce a coloraberration. Electrons converged by the objective lens are made to forman image on the FA by the intermediate lens, and the image is magnifiedand projected by the projection lens, and formed on a secondary electrondetector (MCP). In this optical system, the NA is placed between theobjective lens and the intermediate lens, and optimized to constitute anoptical system capable of reducing an off-axis aberration.

To correct a production-related error of the electro-optical system, andan astigmatic aberration and an anisotropic magnification of an imageoccurring with passage through an E×B filter (Wien filter), anelectrostatic octupole (STIG) is placed to make a correction, and anaxial shift is corrected with a deflector (OP) placed between lenses. Inthis way, a projection type optical system with a uniform resolution inthe visual field can be achieved.

The optical system will be further described using a few embodiments.

(1) Embodiment 5

FIG. 32 shows an electro-optical system. Primary electrons emitted froman electron gun 32•1 pass through an image formation lens 32•2, then atwo-stage zoom lens 32•3 and then a three-stage quadrupole 32•4, and aredeflected at 35° by an E×B filter 32•5, and applied to the samplesurface through an objective lens 32•7 in an opposite direction inparallel to the optical axis of a secondary optical system 32•6.Furthermore, for the quadrupole lens, a multipole lens having two ormore poles may be used, and not only a lens having an even number ofpoles but also a lens having an odd number of poles may be used.Furthermore, the quadrupole lens has 3 to 20 stages, preferably 3 to 10stages, more preferably 3 to 5 stages.

Secondary electrons, reflection electrons and back-scattered electronsemitted from the sample surface with irradiation of primary electronbeam are made to form an image at the center of the E×B filter 32•5 bythe objective lens 32•7, subjected to scaling by an intermediate lens32•8, and then made to form an image just before a projection lens 32•9.The image formed with the intermediate lens 32•8 is magnified by afactor of about 30 to 50 by the projection lens 32•9 and formed on thedetector surface 32•10.

The image formation lens 32•2 enables an image to be formed just beforethe zoom lens 32•3 even if the accelerating voltage is changed, and isconstituted by a one-stage lens in FIG. 32, but may be constituted by amultiple-stage lens.

If the accelerating voltage of primary electron beam is fixed, theirradiation area and shape of primary electron beam on the samplesurface almost depends on the conditions of the zoom lens 32•3 and theconditions of the quadrupole lens 32•4. The zoom lens 32•3 changes theirradiation area during maintaining the beam shape. The quadrupole lens32•4 can change the size of the beam, but is used mainly to change thebeam shape (length-to-width ratio of ellipse). FIG. 32 shows thetwo-stage zoom lens 32•3 and the three-stage quadrupole lens 32•4, butthe number of stages may be increased.

The case will be discussed below where the size of one pixel of thedetector is 16 μm×16 μm, and the size of the detector is 2048×512pixels. When the magnification of the secondary optical system 32•6 is160×, the size on the sample equivalent to one pixel is 16 μm÷160=0.1μm, and the observation area is 204.8×51.2 μm. The irradiation areacovering the observation area has an elliptic shape, and thus changes ina variety of ways depending on the ratio between the long axis and theshort axis of the ellipse. This situation is shown in FIG. 33. In FIG.33, the horizontal axis shows the position of the long axis and thelongitudinal axis shows the position of the short axis. In considerationof the optimum irradiation shape, it is not desired that the beam isapplied to areas other than an observation area 33•1. To achieve theoptimum irradiation shape, an irradiation shape with the largestirradiation efficiency obtained by dividing the area of the observationarea by the area of the irradiation area should be found.

FIG. 34 shows a plot of the ratio of the long axis to the short axis inthe shape of the irradiation area versus the irradiation efficiency.From this plot, it can be understood that a shape with the bestirradiation efficiency is provided when the ratio of the long axis tothe short axis in the irradiation elliptic shape equals the ratio of thelong axis to the short axis in the rectangular observation area. Thatis, a beam shape for thoroughly irradiating the observation area of204.8×51.2 μm is a beam shape of 290×72.5 μm. In fact, the shape of theirradiation beam slightly grows due to influences of the aberration ofthe irradiation optical system and illuminance unevenness of theelectron gun. To achieve this irradiation beam shape, the quadrupolelens 32•4 may be adjusted so that an image just before the quadrupolelens 32•4 forms an elliptic irradiation area on the sample surface by anoptical system including the quadrupole lens 32•4 and the objective lens32•7. In this case, it is only required that a necessary irradiationarea and a sufficiently uniform irradiation current density over theentire irradiation area should be obtained, and it is not necessary tomake the irradiation beam form an image on the sample surface. The sizeof the image just before the quadrupole lens 32•4 is adjusted with thezoom lens 32•3 so that a predetermined irradiation area can be obtainedon the sample surface.

Now, for example, assume that the magnification of the secondaryelectro-optical system 32•6 is changed from 160× to 320×. At this time,the size equivalent to one pixel on the sample surface is 0.05 μm×0.05μm (16 μm÷320=0.05 μm), and the observation area is 102.4×25.6 μm. Ifthe irradiation area is kept at a magnification of 160× in this state,the amount of a signal reaching one pixel of the detector isproportional to the area ratio, and therefore equals ¼ of the signalamount when the magnification is 160×. Provided that an image of asignal amount corresponding to average 400 electrons per pixel is seenwhen the magnification is 160×, the standard deviation of fluctuationsby shot noises at this time is √(400)=20. Accordingly, the S/N ratio is400/20=20. To obtain an image of the same S/N ratio when themagnification is 320×, the same signal amount should be within onepixel. The area per pixel on the sample is ¼ of the original area, andaccordingly the secondary electron signal amount density per unit areashould be quadrupled.

If landing energy represented as a difference in acceleration energy ofprimary electrons and the potential of the sample surface is fixed, theirradiation current density is approximately proportional to thesecondary electron signal amount density. Thus, it can be understoodthat the irradiation current density should be quadrupled. To quadruplethe irradiation current density, the irradiation current should besimply quadrupled, or the irradiation area should be reduced to ¼ of theoriginal area. To reduce the irradiation area to ¼ of the original area,the irradiation size should be reduced to ½ of the original size forboth the long and short axes. Since both the observation area andirradiation area are analogously scaled down by a factor of 2, theobservation area can be sufficiently irradiated.

As means for increasing the irradiation current density, the irradiationcurrent may be increased, or the irradiation area may be decreased.However, it is more desirable that the irradiation area is reduced,taking it consideration that areas other than the observation area arepreferably prevented from being irradiated.

Table 3 shows the voltages of the primary optical system lens and theobtained irradiation sizes on the sample for secondary optical systemmagnifications of 320× and 160×, respectively. As a result, anirradiation area capable of sufficiently keeping up with the secondaryoptical system magnification can be obtained. Although not shown inTable 3, the irradiation size for the magnification of 80× may be anellipse of 620 μm×180 μm, and the irradiation size for the magnificationof 480× may be an ellipse of 100 μm×30 μm. In this way, it is desirablethat the irradiation size is changed according to a change or shift inmagnification.

TABLE 3 Magnification Magnification of 160× of 320× Zoom Lens (V) ZL1−1960 −1390 ZL2 −1020 −1300 Quadrupole lens (V) QL1x 640 → QL1y −640 →QL2x −490 → QL2y 490 → QL3x 70 → QL3y −70 → Irradiation size (μm) x 310155 y 90 50

If the observation area is illuminated with an electron beam, a methodin which a plurality of electron beams each having an area smaller thanthe observation area are scanned to illuminate the observation area canbe used other than the method in which the observation area isilluminated with a rectangular or elliptic electron beam having an areacovering the entire observation area. The number of beams is 1 to 1000,preferably 2 to 100, more preferably 4 to 40. A linear beam with two ormore beams linked together may be scanned. In this case, by scanning thebeam in a direction perpendicular to the long direction of the line, awider area can be inspected with one scan. In this case, the CCD or TDImay be used for the detector. To form a linear beam, for example, anelectron source of LaB6 is used, and the beam is made to pass through alinear slit in the optical system. Furthermore, a cathode with anelectron source having a sharp and slender leading end may be used toform a linear beam. Furthermore, the stage is moved continuously orintermittently in at least one of directions of the XY plane during scanof the beam so that the entire inspection area is covered.

(2) Embodiment 6

FIG. 35 shows the configuration of a detection system using a relaylens. Secondary electrons made to form an image on the surface of an MCP(micro-channel plate) 35•1 in the secondary optical system are amplifiedaccording to a voltage applied to between the electron incidence surfaceand the emission surface of the MCP 35•1 while passing through a channelin the MCP 35•1. The structure and operation of the MCP 35•1 are wellknown, and thus are not described in detail here. In this embodiment,the pixel size on the MCP 35•1 is 26 μm, and the diameter of the channelin an effective area of 1024 pixels wide and 512 pixels long is 6 μm.Electrons amplified in the MCP 35•1 are emitted from the emissionsurface of the MCP 35•1, and enter a fluorescent screen 35•3 coated onan opposite glass plate 35•2 having a thickness of about 4 mm togenerate fluorescence having an intensity consistent with the amount ofelectron signal. Since a thin transparent electrode is coated betweenthe glass plate 35•2 and the fluorescent screen 35•3 and a voltage ofabout 2 to 3 kV is applied to between the electrode and the MCP emissionsurface, expansion of electrodes between the MCP and the fluorescentscreen is restricted as much as possible to avoid the blur of the image.Further, since electrons emitted from the MCP 35•1 enter the fluorescentscreen 35•3 with appropriate energy, luminous efficiency is improved.Furthermore, the materials of the transparent electrode and the glassplate 35•2 coated with the fluorescent screen 35•3 may be any materialsas long as they allow light to pass efficiently.

A light intensity signal, into which an electric signal is converted onthe fluorescent screen 35•3, passes through the glass plate 35•2, thenthrough an optically transparent plate 35•4 insulating vacuum from theatmosphere, then through a relay lens 35•5 imaging light generated onthe fluorescent screen 35•3, and enters a light receiving surface 35•6of a CCD or TDI sensor placed at the imaging position. In thisembodiment, the relay lens 35•5 has an imaging scale factor of 0.5, anda transmittance of 2%.

Light impinging on the light receiving surface 35•6 is converted into anelectric signal by the CCD or TDI sensor, and the electric signal of theimage is outputted to an uptake apparatus. The TDI sensor used in thisembodiment has a pixel size of 13 μm, 2048 horizontal effective pixels,144 integration stages, and 8 taps and a maximum line plate of 83 kHz,but a TDI sensor having a larger number of horizontal effective pixelsand integration stages may be used in view of technological advance ofthe TDI sensor in the future. Furthermore, the structure and operationof the TDI sensor are known, and thus are not described in detail here.

In Table 4, the secondary electron emission current density, thesecondary optical system imaging scale factor, the number of pixelincident electrons obtained when the TDI line rate is determined, theTDI gray scale pixel tone value and the stage speed in this embodimentare shown in the columns of the Embodiment 1.

TABLE 4 Example 1 Example 2 Number of integration stages 144 512 Linerate (Hz) 1.0E+04 3.0E+05 Emission secondary electron 3.5 610 currentdensity (A/m²) Secondary optical system 0.01 0.046 transmittanceSecondary optical system image 260 320 scale MCP aperture ratio 0.6 0.6MCP gain 1.8E+04 4.5E+01 MCP output current (A)  2.0E−0.6  2.0E−0.6Fluorescent screen light emission 8.7E−06 8.7E−06 intensity (W) Relaylens imaging scale factor 0.5 — Relay lens transmittance 0.02 — FOPmagnification — 1 FOP transmittance — 0.4 Incident energy density(nJ/cm²) 0.079 0.004 TDI Responsivity (DN/(nJ/cm²)) 246 9000 Gray scalepixel tone value (DN) 19.4 39.1 Number of incident electrons per 18.9448.3 unit (electrons/pixel) Stage speed (m/s) 0.001 0.015The full scale of the gray scale pixel tone value described here is 255DN. This is due to the fact that the current MCP dynamic range is nomore than 2 μA. An epoch-making improvement in MCP dynamic range cannotbe currently expected, and therefore to obtain a certain pixel tonevalue, it is important that minimum 200 DN/(nJ cm²) of TDI responsivityis ensured.

(3) Embodiment 7

FIG. 36 shows the configuration of a detection system using an FOP. Thestructure and operation of a fluorescent screen 36•1 and the like arethe same as those of the embodiment 5. However, the effective area of anMCP 36•2 in this embodiment has a pixel size of 16 μm, which isequivalent to 2048 (wide)×512 (long) pixels. Unlike the embodiment 5, afluorescent screen 36•11 is coated on an FOP (fiber optic plate) 36•3having a thickness of about 4 mm, instead of the glass plate. A lightintensity signal, into which an electric signal is converted at thefluorescent screen 36•1, passes through fibers of the FOP 36•3. Thelight emission surface of the FOP 36•3 is coated with a transparentelectrode, and this provides a ground potential. Light emitted from theFOP 36•3 passes through another FOP 36•4 with the thickness of, forexample, 3 mm contacting the FOP 36•3 with no gap therebetween, andenters the light receiving surface of a CCD or TDI sensor 36•5 placed onthe light emission surface of the FOP 36•4 via an optically transparentadhesive. Since light is not scattered over fibers of the FOP, imagequality is not significantly influenced if the pixel size of the CCD orTDI sensor 36•5 is sufficiently larger than the fiber diameter.

In this embodiment, the fiber diameter of the FOP is 6 μm, and the pixelsize of the TDI sensor 36•5 is 16 μm. By making the incidence side andthe emission side of the FOP have different fiber diameters, themagnification of the image can be changed, but this causes deformationand distortion to grow, and therefore the fiber diameters are the samein this embodiment. The transmittance is about 40% in this embodiment.

The CCD or TDI sensor 36•5 is placed under vacuum, and an electricsignal 36•6 of the image, into which an optical signal is converted, isoutputted to an uptake apparatus through a field through 36•7 insulatingthe atmosphere from vacuum.

The CCD or TDI sensor 36•5 may be placed under the atmosphere, and theatmosphere may be insulated from vacuum by the FOP, but in considerationof reduction in transmittance and growth of deformation with an increasein thickness of the FOP, such a configuration is less likely positivelyadopted.

The TDI sensor 36•5 used in this embodiment has a pixel size of 16 μm,2048 horizontal effective pixels, 512 integration stages, and 32 tapsand a maximum line plate of 300 kHz, but a TDI sensor having a largernumber of horizontal effective pixels and integration stages may be usedin view of technological advance of the TDI sensor in the future.

The secondary electron emission current density, the secondary opticalsystem imaging scale factor, the number of pixel incident electronsobtained when the TDI line rate is determined, the TDI gray scale pixeltone value and the sage speed in this embodiment are shown in thecolumns of the embodiment 2 in Table 4.

(4) Embodiment 8

FIG. 37(A) schematically shows the configuration of a projectionelectron microscope type defect inspection apparatus EBI, and FIG. 37(B)schematically shows the configurations of a secondary optical system anda detection system of the defect inspection apparatus EBI. In FIG. 37,an electron gun 37•1 has a thermal electron emitting LaB₆ cathode 37•2capable of operating under a large current, and primary electronsemitted in a first direction from the electron gun 37•1 pass through aprimary optical system including a several-stage quadrupole lens 37•3 tohave the beam shape adjusted, and then pass through a Wien filter 37•4.The traveling direction of primary electrons is changed to a seconddirection by the Wien filter 37•4 so that they are inputted to a sampleW as an inspection object. Primary electrons leaving the Wien filter37•4 and traveling in the second direction have the beam diameterreduced by an NA aperture plate 37•5, pass through an objective lens37•6, and is applied to the sample W.

In this way, in the primary optical system, a high luminance electrongun made of LaB₆ is used as the electron gun 37•1, and thus making itpossible to obtain a primary beam having a large current and a largearea with low energy compared to the conventional scanning defectinspection apparatus. The electron gun 37•1 is made of LaB₆, has atruncated conic shape and a diameter of 50 μm or greater, and canextract electrons at an intensity of 1×10³ A/cm²sr to 1×10⁸ A/cm²sr at aprimary electron draw voltage of 4.5 kV. The intensity is preferably1×10⁶ A/cm²sr to 1×10⁷ A/cm²sr at 4.5 kV. The intensity is furtherpreferably 1×10⁶ A/cm²sr to 1×10⁷ A/cm²sr at 10 kV. Furthermore, theelectron gun 37•1 can also extract electrons at an intensity of 1×10⁶A/cm²sr to 2×10¹⁰ A/cm²sr at a primary electron extraction voltage of4.5 kV as a shot key type. The intensity is preferably 1×10⁶ A/cm²sr to5×10⁹ A/cm²sr at 10 kV. Furthermore, a shot key type made of ZrO may beused for the electron gun 37•1.

The shape of an irradiation area in which primary electrons are appliedto the sample W is approximately symmetric to two other orthogonal axesnot including the optical axis of primary electrons, unevenness inilluminance of primary electrons in the area in which primary electronsare applied to the sample is 10% or less, preferably 5% or less, morepreferably 3% or less, thus being very uniform. In this case, the beamshape may be used even if the shape is not approximately symmetric totwo other orthogonal axes not including the optical axis of primaryelectrons as described above.

In this embodiment, the sample W is irradiated with a plane beam havingthe cross section formed into, for example, a rectangular shape of 200μm×50 μm, thus making it possible to irradiate a small area having apredetermined area on the sample W. To scan the sample W with the planebeam, the sample W is placed on a high accuracy XY stage (not shown)accommodating, for example, 300 mm wafer, and two-dimensionally moved onthe XY stage with the plane beam fixed. Furthermore, since it is notnecessary to concentrate primary electrons onto a beam spot, the planebeam has a low current density, and the sample W is not significantlydamaged. For example, the current density of the beam spot is 10 A/cm²to 10⁴ A/cm² the conventional beam scanning detect inspection apparatus,while the current density of the plane beam is only 0.0001 A/cm² to 0.1A/cm² in the defect inspection apparatus of FIG. 37. The current densityis preferably 0.001 A/cm² to 1 A/cm². The current density is morepreferably 0.01 A/cm² to 1 A/cm². On the other hand, the dose is 1×10⁻⁵C/cm² in the conventional beam scanning system, while it is 1×10⁻⁶ C/cm²to 1×10⁻¹ C/cm² in the system of this embodiment, and the system of thisembodiment has a higher sensitivity. The dose is preferably 1×10⁻⁴ C/cm²to 1×10⁻¹ C/cm², further preferably 1×10⁻³ C/cm² to 1×10⁻¹ C/cm².

The incident direction of the primary electron beam is basically the Edirection of E×B 37•4, i.e. a direction of an electric field, theintegration direction of the TDI and the direction of movement of thestage are made to match this direction. The incident direction of theprimary electron beam may be the B direction, i.e. a direction in whicha magnetic field is applied.

Secondary electrons, reflection electrons and back-scattered electronsare generated from the area of the sample W irradiated with primaryelectrons. First, for explanation of detection of secondary electrons,secondary electrons emitted from the sample W are magnified by theobjective lens 37•6 and pass through the NA aperture plate 37•5 and theWien filter 37•4 so as to travel in a direction opposite to the seconddirection, and are then magnified again by an intermediate lens 37•7,and further magnified by a projection lens 37•8 and enter a secondaryelectron detection system 37•9. In the secondary optical system 37•9guiding secondary electrons, the objective lens 37•6, the intermediatelens 37•7 and the projection lens 37•8 are all high accuracyelectrostatic lenses, and the magnification of the secondary opticalsystem is variable. Primary electrons are made to impinge on the sampleW at almost a right angle (±5 or less, preferably ±3 or less, morepreferably ±1 or less), and secondary electrons are taken out at almosta right angle, so that shades by irregularities on the surface of thesample W never occur.

The Wien filter 37•4 is also called an E×B filter, has an electrode anda magnet, has a structure in which the electric field is orthogonal tothe magnetic field, and has a function of bending primary electrons at,for example, 35° to the sample direction (direction perpendicular to thesample) while moving in a straight line at least one of the secondaryelectron, the reflection electron and the back-scattered electron fromthe sample.

The secondary electron detection system 37•9 receiving secondaryelectrons from the projection lens 37•8 comprises a micro-channel plate(MCP) 37•10 propagating incident secondary electrons, a fluorescentscreen 37•11 converting electrons leaving the MCP 37•10 into light, anda sensor unit 37•12 converting light leaving the fluorescent screen37•11 into an electric signal. The sensor unit 37•12 has a highsensitivity line sensor 37•13 comprised of a large number of solidimaging devices two-dimensionally arranged, fluorescence emitted fromthe fluorescent screen 37•11 is converted into an electric signal by theline sensor 37•13, the electric signal is sent to an image processingunit 37•14, and processed in parallel, in multistage and at a highspeed.

While the sample W is moved to have individual areas on the sample Wirradiated with a plane beam and scanned in order, the image processingunit 37•14 accumulate data about the XY coordinates and images of areasincluding defects one after another, and generate an inspection resultfile including the coordinates and images of all areas of the inspectionobject including defects for one sample. In this way, inspection resultscan be collectively managed. When this inspection result file is read, adefect distribution and a detailed defect list of the sample aredisplayed on a display of the image processing unit 12.

Actually, of various kinds of components of the defect inspectionapparatus EBI, the sensor unit 37•12 is placed under an atmosphere, butother components are placed in a column kept under vacuum, and thereforein this embodiment, a light guide is provided on an appropriate wallsurface of the column, and light emitted from the fluorescent screen37•11 is taken out into the atmosphere via the light guide and passed tothe line sensor 37•13.

Provided that the amount of elections emitted from the sample W is 100%,the ratio of electrons that can reach the MCP 37•10) (hereafter referredto as “transmittance”) is expressed by the following equation:transmittance(%)=(amount of electrons that can reach MCP 37•10)/(amountof electrons emitted from sample W)×100.The transmittance depends on the aperture area of the NA aperture plate37•5. As an example, a relation between the transmittance and theaperture diameter of the NA aperture plate is shown in FIG. 38.Actually, at least one of the secondary electron, the reflectionelectron and the back-scattered electron generated from the sample reachthe electron detection system D in the ratio of 200 to 1000 electronsper pixel.

The center of the image projected under magnification and formed on thedetector, and the center of the electrostatic lens are on a common axis,the electron beam has the common axis as an optical axis between adeflector and the sample, and the optical axis of the electron beam isperpendicular to the sample.

FIG. 39 shows a specific example of the configuration of the electrondetection system 37•9 in the defect inspection apparatus EBI of FIG. 37.A secondary electron image or reflection electron image 38•1 is formedon the incident surface of the MCP 37•10 by the projection lens 37•8.The MCP 37•10 has, for example, a resolution of 6 μm, a gain of 10³ to10⁴, and 2100×520 active pixels, and propagates electrons according tothe electron image 39•1 to irradiate the fluorescent screen 37•11.Consequently, fluorescence is emitted from areas of the fluorescentscreen 37•11 irradiated with electrons, and the emitted fluorescence isdischarged into the atmosphere via the light guide 39•2 of lowdeformation (e.g. 0.4%). The discharged fluorescence is made to enterthe line sensor 37•13 via an optical relay lens 39•3. For example, theoptical relay lens 39•3 has a magnification of ½, a transmittance of2.3%, and a deformation of 0.4%, and the line sensor 37•13 has 2048×512pixels. The optical relay sensor 39•3 forms an optical image 39•4matching the electron image 39•1 on the incident surface of the linesensor 37•1. An FOP (fiber optic plate) may be used instead of the lightguide 39•2 and the relay lens 39•3, and the magnification in this caseis 1. Furthermore, if the number of electrons per pixel is 500 orgreater, an MCP may be omitted.

The defect inspection apparatus EBI shown in FIG. 37 can be operated inone of a positive charge mode and a negative charge mode for secondaryelectrons by adjusting an acceleration voltage of the electron gun 37•1and a sample voltage applied to the sample W and using the electrondetection system 37•9. Further, by adjusting the acceleration voltage ofthe electron gun 37•1, the sample voltage applied to the sample W andobjective lens conditions, the defect inspection apparatus EBI can beoperated in a reflection electron imaging mode in which high energyreflection electrons emitted from the sample W by irradiation of primaryelections is detected. The reflection electrode has energy the same asthe energy with which the primary electron enters the sample W, and hasa higher level of energy than that of the secondary electron, and istherefore hard to be influenced by a potential by charge of the samplesurface or the like. For the electron detection system, an electronimpact detector such as an electron impact CCD or electron impact TDIoutputting an electric signal matching the intensity of secondaryelectrons or reflection electrons may also be used. In this case, theMCP 37•10, the fluorescent screen 37•11 and the relay lens 39•3 (or FOP)are not used, but the electron impact detector is installed at theimaging position and used. This configuration enables the defectinspection apparatus EBI to operate in a mode suitable for theinspection object. For example, the negative charge mode or reflectionelectron imaging mode may be used to detect defects of metal wiring,defects of gate contact (GC) wiring or defects of a resist pattern, andthe reflection electron imaging mode may be used to detect poorconduction of a via or residues on the bottom of the via after etching.

FIG. 40(A) illustrates requirements for operating the defect inspectionapparatus EBI of FIG. 37 in the above three modes. The accelerationvoltage of the electron gun 37•1 is V_(A), the sample voltage applied tothe sample W is V_(W), irradiation energy of primary electrons when thesample is irradiated is E_(IN), and signal energy of secondary electronsimpinging upon the secondary electron detection system 37•9 is E_(OUT).The electron gun 37•1 is configured so that the acceleration voltageV_(A) can be changed, the variable sample voltage V_(W) is applied tothe sample W from an appropriate power supply (not shown). Then, if theacceleration voltage V_(A) and the sample voltage V_(W) are adjusted andthe electron detection system 37•9 is used, the defect inspectionapparatus EBI can operate in the positive charge mode in a range where asecondary electron yield is greater than 1, and operate in the negativecharge mode in a range where the secondary electron yield is less than 1as shown in FIG. 40(B). Furthermore, by setting the acceleration voltageV_(A), the sample voltage V_(W) and the objective lens conditions, thedefect inspection apparatus EBI can use a difference in energy betweenthe secondary electron and the reflection electron to distinguishbetween the two types of electrons, and thus can operate in thereflection electron imaging mode in which only reflection electrons aredetected.

One example of values of V_(A), V_(W), E_(IN) and E_(OUT) for operatingthe defect inspection apparatus EBI in the reflection electron imagingmode, the negative charge mode and the positive charge mode will bedescribed below.

Reflection Electron Imaging Mode

V_(A)=−4.0 kV±1° V (preferably ±0.1°, more preferably ±0.01° or less).

V_(W)=−2.5 kV±1° V (preferably ±0.1°, more preferably ±0.01° or less).

E_(IN)=1.5 keV±1° V (preferably ±0.1°, more preferably ±0.01° or less).

E_(out)=4 keV or less.

Negative Charge Mode

V_(A)=−7.0 kV±1 V (preferably ±0.1V, more preferably ±0.01V or less).

V_(W)=−4.0 kV±1V (preferably ±0.1V, more preferably ±0.01V or less).

E_(IN)=3.0 keV±1V (preferably ±0.1V, more preferably ±0.01V or less).

E_(out)=4 keV+α (α: energy width of secondary electrons).

Positive Charge Mode

V_(A)=−4.5 kV±1V (preferably ±0.1V, more preferably ±0.01V or less).

V_(W)=−4.0 kV±1V (preferably ±0.1V, more preferably ±0.01V or less).

E_(IN)=0.5 keV±1V (preferably ±0.1V, more preferably ±0.01V or less).

E_(out)=4 keV+α (α: energy width of secondary electrons).

As described above, principally, a fixed potential of 4 kV±10V(preferably 4 kV±1 V, more preferably 4 kV±0.01V or less) is applied asa potential V_(W) for both the positive charge mode and negative chargemode in the case of the secondary electron mode. On the other hand, inthe case of the reflection electron mode, the acceleration potentialV_(A) is set to 4 kV±10V (preferably 4 kV±1V, more preferably 4 kV±0.01Vor less), and the sample potential V_(W) is set to any potential lowerthan the acceleration potential of 4 kV or less. In this way, secondaryelectrons or reflection electrons as a signal impinge on the MCP as adetector with optimum energy of 4 keV±10 eV+α (preferably 4 keV±1 eV,more preferably 4 keV±0.01 eV).

The way of setting potentials described above corresponds principally tothe case where energy of signal electrons made to pass through thesecondary optical system is set to 4 keV, and an electron image on thesample surface is formed on the detector, and by changing this energy,the set potentials in the secondary electron mode and reflectionelectron mode can be changed to obtain an electron image appropriate tothe type of sample. For the negative charge mode, an area of electronirradiation energy lower than that of a positive charge area of FIG. 40(B) (e.g. 50 eV or less) can be used.

Actually, the detected amounts of secondary electrons and reflectionelectrodes vary with surface compositions of inspected areas on thesample W, pattern shapes and surface potentials. That is, the yield ofsecondary electrons and the mount of reflection electrons vary dependingon the surface composition of the inspection object on the sample W, andthe yield of secondary electrons and the amount of reflection electronsare greater in pointed areas or corners of the pattern than in planeareas. Furthermore, if the surface potential of the inspection object onthe sample W is high, the amount of emitted secondary electronsdecreases. In this way, the intensities of electron signals obtainedfrom secondary electrons and reflection electrons detected by thedetection system 37•9 vary with the material, the pattern shape and thesurface potential.

2-3-3) E×B Unit (Wien Filter)

The Wien filter is a unit of an electromagnetic prism optical systemhaving an electrode and a magnetic pole placed orthogonally to eachother to orthogonalize an electric field and a magnetic field. Ifelectric and magnetic fields are selectively provided, an electron beamimpinging thereupon in one direction is deflected, and an electron beamimpinging in a direction opposite thereto can create conditions in whicheffects of a force received from the electric field and a force receivedfrom the magnetic field are offset (Wien conditions), whereby a primaryelectron beam is deflected and applied onto a wafer at a right angle,and a secondary electron beam can travel in a straight line toward adetector.

The detailed structure of an electron beam deflection unit of an E×Bunit will be described using FIG. 41 and FIG. 42 showing a longitudinalplane along the A-A line of FIG. 41. As shown in FIG. 41, a field of anelectron beam deflection unit 41•2 of an E×B unit 41•1 has a structurein which an electric field and a magnetic field are orthogonalized in aplane perpendicular to the optical axis of a projection optical unit,i.e. E×B structure. Here, the electric field is generated by electrodes41•3 and 41•4 each having a concave curved surface. The electric fieldgenerated by the electrodes 41•3 and 41•4 is controlled by control units41•5 and 41•6, respectively. On the other hand, electromagnetic coils41•7 and 41•8 are placed in such a manner that they are orthogonal tothe electrodes 41•3 and 41•4 for generating electric fields, wherebymagnetic fields are generated. Furthermore, the electrodes 41•3 and 41•4for generating electric fields is point-symmetric, but they may beconcentric.

In this case, to improve uniformity of the magnetic field, pole pieceshaving parallel and plain shapes are provided to form a magnetic path.The behavior of the electron beam in the longitudinal plane along theA-A line is as shown in FIG. 42. Applied electron beams 42•1 and 42•2are deflected by electric fields generated by the electrodes 41•3 and41•4 and magnetic fields generated by electromagnetic coils 41•7 and41•8, and then enter the sample surface at a right angle.

Here, the position and angle at which the irradiation electron beams42•1 and 42•2 enter the electron beam deflection unit 41•2 are uniquelydetermined when energy of electrons is determined. Further, controlunits 41•5, 41•6, 41•9 and 41•10 control electric fields generated bythe electrodes 41•3 and 41•4 and magnetic fields generated by theelectromagnetic coils 41•7 and 41•8 so that secondary electrons 42•3 and42•4 travel in a straight line. i.e. the requirement for the electricfield and magnetic filed of v×B=E is met, whereby secondary electronstravel in straight line through the electron beam deflection unit 41•2,and impinge on the projection optical system. Here, v represents thespeed of the electron (m/s), B represents the magnetic field (T), erepresents the amount of electric charge (C), and E represents theelectric field (V/m).

Here, the E×B filter 41•1 is used for separation of primary electronsand secondary electrons, but the magnetic field can be used for theseparation as a matter of course. Furthermore, only the electric fieldmay be used to separate primary electrons and secondary electrons.Further, it may be used to separate primary electrons and reflectionelectrons as a matter of course.

Now, as the embodiment 9, an alteration example of the E×B filter willbe described with reference to FIG. 43. FIG. 43 is a sectional viewtaken along a plane perpendicular to the optical axis. Four pairs ofelectrodes 43•1 and 43•2, 43•3 and 43•4, 43•5 and 43•6, and 43•7 and43•8 for generating electric fields are formed by a nonmagneticconductive material, are cylindrical as a whole, and are fixed withscrews (not shown) on the inner surface of an electrode supportingbarrel 43•9 made of insulating material, or the like. The axis of theelectrode supporting barrel 43•9 and the axis of the cylinder formed byelectrodes are made to match an optical axis 43•10. A groove 43•11parallel to the optical axis 43•10 is provided on the inner surface ofthe electrode supporting barrel 43•9 between the electrodes 43•1 to43•8. The area of the inner surface is coated with a conductive material43•12, and set at an earth potential.

If a voltage proportional to “cos θ1” is given to the electrodes 43•3and 43•5, a voltage proportional to “−cos θ1” is given to the electrodes43•6 and 43•4, a voltage proportional to “cos θ2” is given to theelectrodes 43•1 and 43•7, and a voltage proportional to “−cos θ2” isgiven to the electrodes 43•8 and 43•2 when electric fields aregenerated, almost uniform parallel electric fields can be obtained in anarea equivalent to about 60% of the inner diameter of the electrode. Theresults of simulation of an electric filed distribution are shown inFIG. 44. Furthermore, four pairs of electrodes are used in this example,but uniform parallel electric fields can be obtained in an areaequivalent to about 40% of the inner diameter even if a three pairs ofelectrodes are used.

Generation of magnetic fields is performed by placing two rectangularplatinum alloy permanent magnets 43•13 and 43•14 in parallel outside theelectrode supporting band 43•9. A raised portion 43•16 composed of amagnetic material is provided around the surfaces of the permanentmagnets 43•13 and 43•14 on the optical axis 43•10 side. This raisedportion 43•16 compensates for outward convex deformation of a magneticline of flux on the optical axis side 43•10, and its size and shape canbe determined by simulation analysis.

A yoke or magnetic circuit 43•15 made of ferromagnetic material isprovided outside the permanent magnets 43•13 and 43•14 so that a channelsituated opposite to the optical axis 43•10 of the magnetic line of fluxby the permanent magnets 43•13 and 43•14 forms a barrel concentric withthe electrode supporting barrel 43•9.

An E×B separator shown in FIG. 43 may be applied not only to theprojection type electron beam inspection apparatus shown in FIG. 25-1but also to a scanning electron beam inspection apparatus.

One example of the scanning electron beam inspection apparatus is shownin FIG. 25-2. An electron beam is applied from an electron gun 25•14 toa sample 25•15. A primary system electron beam passes through an E×B25•16, but travels in a straight line with no deflection force exertedthereon at the time of incidence, is focused by an objective lens 25•17,and enters the sample 25•15 at almost a right angle. Electrons exitingfrom the sample 25•15 are guided to a detector 25•18 with a deflectionforce exerted thereon by the E×B 25•16. In this way, by adjusting anelectric field and a magnetic field of the E×B 25•16, one of chargedparticle beams of the primary system and the secondary system can bemade to travel in a straight line, with the other traveling in astraight line in any direction.

Furthermore, if the E×B 25•16 is used, the deflection force is exertedto cause an aberration in a direction of deflection, and therefore anE×B deflector may be further provided between the electron gun 25•14 ofthe primary system optical system and the E×B 25•16 for correcting theaberration. Furthermore, for the same purposes, the E×B detector may befurther provided between the detector 25•18 of the secondary system andthe E×B 25•16.

In the scanning electron beam inspection apparatus or scanning electronmicroscope, finely focusing with the primary system electron beam leadsto an improvement in resolution and therefore generally, the primarysystem electron beam is made to travel in a straight line as shown inFIG. 25•2 with no excessive reflection force exerted on the primaryelectron beam, and the secondary beam is deflected. However, ifconversely, it is more preferable that the primary beam is deflected andthe secondary beam is made to travel in a straight line, such aconfiguration may be adopted. Similarly, in the projection type electronbeam inspection apparatus, it is generally preferable that a deflectionforce causing no aberration is not given to the secondary beam to matchimaging areas on the sample with pixels on a CCD of the detector. Thus,generally, the primary beam is deflected and the secondary beam is madeto travel in a straight line as shown in FIG. 25-1, but if it is morepreferable that the primary beam is made to travel in a straight lineand the secondary beam is deflected, such a configuration may beadopted.

Furthermore, the intensities of the electric field and the magneticfield of E×B may be set differently for each mode of the secondaryelectron mode and the reflection electron mode. The intensities of theelectric field and the magnetic field can be set so that an optimumimage can be obtained for each mode. When it is not required that theset intensity should be changed, the intensity may be kept a constantlevel as a matter of course.

As apparent from the above description, according to this example, boththe electric field and magnetic field can take uniform areassufficiently around the optical axis, and the irradiation range of theprimary electron beam is expanded, the aberration of the image made topass the E×B separator can be kept at an uninfluential level.Furthermore, since the raised portion 43•16 is provided in the peripheryof the magnetic pole forming the magnetic field, and the magnetic poleis provided outside an electric field generating electrode, a uniformmagnetic field can be generated, and deformation of the electric fieldby the magnetic pole can be reduced. Furthermore, since a permanentmagnet is used to generate the magnetic field, the overall E×B separatorcan be contained in a vacuum. Further, the electric field generatingelectrode and a magnetic path forming magnetic circuit have concentriccylindrical shapes having an optical axis as a central axis, whereby theoverall E×B separator can be downsized

2-3-4) Detector

A secondary electron image from a wafer, which is formed in thesecondary optical system, is first amplified by a micro-channel plate(MCP), then enters a fluorescent screen, and is converted into anoptical image. As principle of the MCP, several millions to several tensof millions of very slender conductive glass capillaries each having adiameter of 1 to 100 μm and a length of 0.2 to 10 mm, preferably adiameter of 2 to 50 μm and a length of 0.2 to 5 mm, more preferably adiameter of 6 to 25 μm and a length of 0.24 to 1.0 mm are bundledtogether to form a thin plate, and by applying a predetermined voltagethereto, each of capillaries acts as an independent secondary electronamplifier, and a secondary electron amplifier is formed as a whole. Theimage converted into light by this detector is projected on the TDI-CCDin a ratio of 1:1 in an FOP system placed under the atmosphere via avacuum transparent window.

Now, the operation of the electro-optical apparatus having theconfiguration described above will be described. As shown in FIG. 25-1,a primary electron beam emitted from the electron gun 25•4 is convergedby the lens system 25•5. The converged primary electron beam is made toenter the E×B-type deflector 25•6, deflected so as to irradiate thesurface of the wafer W at a right angle, and made to form an image onthe surface of the wafer W by the objective lens system 25•8.

Secondary electrons emitted from the wafer by irradiation of the primaryelectron beam are accelerated by the objective lens 25•8, enters theE×B-type deflector 25•6, and travels though the deflector in a straightline, and is guided through the lens system 25•10 of the secondaryoptical system to the detector 25•11. The secondary electrons are thendetected by the detector 25•11, and a detection signal thereof is sentto the image processing unit 25•12. Furthermore, a high voltage of 10 to20 kV is applied to the objective lens 25•7, and the wafer is placed.

Here, if the wafer W has the via 25•13, the electric field of theelectron beam irradiation surface of the wafer is 0 to −0.1 V/mm (−indicates a high potential at the wafer W side) provided that thevoltage given to the electrode 25•8 is −200 V. In this state, nodischarge occurs between the objective lens system 25•7 and the wafer W,and the defect inspection for the wafer W can be performed, butefficiency of detection of secondary electrons is slightly reduced.Thus, a series of operations for irradiating an electron beam to detectsecondary electrons are carried out, for example, four times, theobtained detection results of the four time operations are subjected toprocessing such as cumulative addition and averaging to obtain apredetermined detection sensitivity.

Furthermore, when the wafer has no via 25•13, no discharge occursbetween the objective lens 25•7 and the wafer, and defect inspection forthe wafer can be performed even if the voltage given to the electrode25•8 is +350 V. In this case, secondary electrons are converged by thevoltage given to the electrode 25•8, and are further converged by theobjective lens 25•7, and thus efficiency of detection of secondaryelectrons in the detector 25•11 is improved. Accordingly, the speed ofprocessing as a wafer defect apparatus is enhanced, and inspection canbe carried out in high throughput.

2-3-5) Power Supply

A power supply unit of the apparatus is mainly comprised of a directcurrent high voltage precision power supply having about severalhundreds output channels for control of electrodes, and has its supplyvoltage varied depending on the role of the electrode and the positionalrelation. In view of demands on resolution and accuracy of images, thepower supply unit is required to have stability in the order of several100 ppm or less, preferably 20 ppm or less, more preferably several ppmor less with respect to the set value. To minimize variations of thevoltage with time and temperature, noise ripples and the like as factorsimpairing stability, and some contrivance is made for a circuit system,selection of parts and implementation.

Types of power supplies other than electrodes include a heating constantcurrent source for a heater, a high-voltage and high-speed amplifier fortwo-dimensionally deflecting a beam to confirm aligning of the beam nearthe center of an aperture electrode when the primary beam is centered, aheating constant current source for a heater, a constant current sourcefor an electromagnetic coil for E×B as an energy filter, a retardingpower supply for applying a bias to a wafer and a power supplygenerating a potential for adsorbing a wafer to an electrostatic chuck,a high-voltage and high-speed amplifier for making an EO (electronoptical) correction, and an MCP power supply amplifying electrons withprinciple of a photomultiplier.

FIG. 45 shows the overall configuration of the power supply unit. Inthis figure, an electric power is supplied to an electrode of a columnportion 45•1 through a connection cable from a power supply rack 45•2and high-speed and high-voltage amplifiers 45•3, 45•4 and 45•5, althoughnot shown in the figure. The high-speed and high-voltage amplifiers 45-3to 45-5 are broadband amplifiers, and deal with signals of highfrequencies (DC-MHz), and therefore they are placed near the electrodeto prevent an increase in electrostatic capacity of a cable in order toinhibit property degradation and an increase in power consumption due tothe electrostatic capacity of the cable. An correction signal isoutputted from an EO correction 45•6, and converted into an voltagehaving a phase and a magnitude matching a vector value for eachelectrode of an octupole at an octupole conversion unit 45•7, and thevoltage is inputted to the high-speed and high-voltage amplifier 45•4,amplified, and then supplied to an electrode included in a column.

An AP image acquisition block 45•8 has a role as an auxiliary functionsuch that a serrate wave is generated from the AP image acquirementblock 45•8 to ensure centering of a beam near the center of an apertureelectrode when a primary beam is centered, and applied to a deflectionelectrode of the column portion 45•1 by the high-speed and high-voltageamplifier. The beam is two-dimensionally deflected, whereby themagnitude of a beam current received at the aperture electrode isrelated to the position, and an image is displayed to set the beamposition to the mechanical central position.

An AF control 46•9 achieves a function such that a voltage correspondingto the best focal condition measured in advance is stored in a memory,the value of the voltage is read according to the stage position, thevoltage is converted into an analog voltage by a D/A converter, thevoltage is applied a focus adjustment electrode included in the columnportion 45•1 through the high-speed and high-voltage amplifier 45•5, andan observation is made while maintaining the optimum focus position.

The direct current high voltage precision power supply having aboutseveral hundreds output channels for control of voltages, comprised ofpower supply groups 1 to 4, is housed in the power supply rack 45•2. Thepower supply rack 45•2 constitutes a system capable of receivingcommands from a CPU unit 45•13 by means of a communication card 45•11,an optical fiber communication 45•12 having electric insulation qualityto ensure safety and prevent occurrence of a grand loop to prevententrance of noises, and the like, by a control communication unit 45•10,and sending a status such as abnormality of power supply apparatus. AUPS 45•14 prevents destruction of apparatus, abnormal discharges, risksto human bodies and the like caused by overrunning of the system whencontrol abnormality occurs due to service interruption and unexpectedpower blockage. A power supply 45•15 is a power reception unit of themain body, and is configured so that safety cooperation can be achievedas an overall inspection apparatus including interlock, currentlimitation and the like.

The communication card 45•11 is connected to a data bus 45•16 and anaddress bus 45•17 of the control CPU unit 45•13, so that real timeprocessing can be carried out.

FIG. 46 shows one example of the circuit configuration of a static highvoltage unipolar power supply (for lens) for a circuit system where astatic DC of several hundreds to several tens kilovolts is produced. InFIG. 46, a signal source 46•1 is caused to generate an alternatingcurrent voltage having a frequency providing an optimum magneticpermeability of a trans 46•2, and the voltage is made to pass through amultiplier 46•3, and then guided to a drive circuit 46•4 to generate avoltage having an amplitude several tens to several hundreds timesgreater by the trans 46•2. A cock craft walten circuit 46•5 is a circuitincreasing a voltage while performing rectification. By combination ofthe trans 46•2 and the cock craft walten circuit 46•5, a desired DCvoltage is obtained, and by a low pass filter 56•6, further flatness isachieved to reduce ripples and noises. A high-voltage output is dividedaccording to the resistance ratio of output voltage detectionresistances 46•7 and 46•8 to obtain a voltage within a range of voltagescapable of being dealt with by a usual electronic circuit. Becausestability of this resistance mostly determines voltage accuracy,elements excellent in temperature stability, long term variations andthe like are used, and in view of the fact that the division ratio isespecially important, measures are taken such that a thin film is formedon the same insulation substrate, or resistance elements are broughtinto close contact with one another so that the temperature does notvary.

The result of the division is compared to the value of a referencevoltage generating D/A converter 46•10 by a calculation amplifier 46•9,and if there is a difference, the output of the calculation amplifier46•9 is increased or decreased, and an AC voltage having an amplitudematching the value thereof is outputted from the multiplier 46•3 to forma negative feedback. Although not shown in the figure, the output of thecalculation amplifier 46•9 is made to be unipolar, or the quadrant ofresponse of the multiplier 46•3 is limited to prevent saturation. Thecalculation amplifier 46•9 requires a very large amplification gain (120dB or greater), and is mostly used in an open loop as an element, andtherefore a low noise operation amplifier is used. The reference voltagegenerating D/A converter 46•10 requires stability equivalent to orhigher than that of the output voltage detection resistances 46•7 and46•8 in terms of accuracy. To generate this voltage, a reference IChaving a constant voltage diode using a hand gap combined with athermostabilization feature using a heater (not shown) is often used,but a Peltier element is used instead of the heater so thatthermostability can be further improved. Furthermore, the Peltierelement may be used in a single or multi-stage for thermostabilizationof the output voltage detection resistances 46•7 and 46•8.

FIG. 47 shows one example of the circuit configuration of a staticbipolar power supply (for aligner or the like). The basic concept issuch that V5 and V6 are generated with a power supply equivalent to thatof the circuit of FIG. 46, and the voltages are used to input commandvalues from a component 47•1 to a linear amplifier constituted bycomponents 47•1 to 47•6 to form a bipolar high-voltage power supply.Generally, the calculation amplifier 47•2 operates at around ±12 V, andtherefore although not shown in the figure, amplification circuits bydiscrete elements are required between the component 47•2 and thecomponents 47•5 and 47•6 to amplify the voltage from ±several volts to±several hundreds to several thousands volts. Notices aboutcharacteristics required for the components 47•1 to 47•4 are the same asthose described with the circuit of FIG. 46.

FIGS. 48 to 50 each show an example of a circuit of a special powersupply, and FIG. 48 shows an example of a circuit for a heater and agun, which is constituted by components 48•1 to 48•4. A voltage source48•1, a resistance 48•3 and a power supply 48•4 are superimposed on abias voltage source 48•2. The power supply 48•4 for a heater isconstituted by a constant current source, the value of an actuallypassing current is detected by the resistance 48•3, and although notshown in the figure, the value is temporarily digitized, isolated withoptical fibers or the like, and sent to the control communication unit45•10. For the setting of the voltage value of the voltage source 48•1,the current value of the power supply 48•4 and the like, the value fromthe control communication unit 45•10 is inversely converted in the sameprinciple, and the value is set for an actual power setting unit.

FIG. 49 shows an example of a power supply circuit for an MCP, which iscomprised of voltage sources 49•1 and 49•2, relay circuits 49•3 and49•4, and current detection circuits 49•5, 49•6 and 49•7. A terminalMCP1 makes measurements from several Pas for measurement of the value ofa current passing into the MCP, and is thus required to have a strictshield structure to prevent entrance of leaked currents and noises. Aterminal MCP2 includes current measurement after amplification by theMCP, and can calculate an amplification gain from the ratio of values ofcurrents passing through the resistances 49•6 and 49•7. The resistance49•5 measures a current on a fluorescent screen. Measurement and settingat the superimposed portion are the same as those at the heater and gun.

FIG. 50 shows an example of a circuit of a constant current source foran E×B magnetic field coil constituted by components 50•1 and 50•2,which generally outputs a current of several hundred mA. Stability ofthe magnetic field as an energy filter is important, and stability inthe order of several ppm is required.

FIG. 51 shows one example of a power supply for a retarding andelectrostatic chuck, which is constituted by components 51•1 to 51•9. Apower supply similar to the static bipolar power supply (for aligner) ofFIG. 46 is superimposed on a bias power supply (for retarding) 51•10.Measurement and setting at the superimposed portion are the same asthose at the heater and gun (FIG. 48).

FIG. 52 shows one example of the hardware configuration of an EOcorrecting deflection electrode, which is constituted by components 52•1to 52•7. An correction signal is inputted to an octupole conversion unit52•4 from an X axis EO correction 52•1 and a Y axis EO correction 52•2,and an output after conversion is sent to a high-speed amplifier 52•5.The voltage is amplified from several tens of volts to several hundredsof volts by the high-speed amplifier 52•5, and then applied to EOcorrection electrodes 52•6 situated at angular intervals of 45°. A ΔXcorrection 52•3 is an input for fine correction such as correction ofmirror bend, and is added to an X signal within the octupole conversionunit 52•4.

FIG. 53 shows one example of the circuit configuration of the octupoleconversion unit, which performs vector operation from signals 53•2,53•3, 53•4 and 53•5 for electrodes 53•1 situated at angular intervals of45° other than X and Y axes, and generate equivalent voltages. Theexample of operation in this case uses values described at components53•6, 53•7, 53•8 and 53•9. This can be achieved by an analog resistancenetwork, or read of the table by a ROM when components 53•6 to 53•9 aredigital signals.

FIG. 54 shows one example of a high-speed and high voltage amplifier,which is constituted by components 54•1 to 54•11. An example of awaveform during output of a short wave is shown in FIG. 54(B). In thisexample, Power Operation Amplifier PA 85A manufactured by APEX Co., Ltd.(U.S.A) is used to form an amplifier, and a bandwidth covering amega-band, an output range of about ±200 V, and a through rate largerthan about 1000 V/μs can be achieved, thus achieving dynamiccharacteristics required for the high-speed and high-voltage amplifier.

2-4) Precharge Unit

As shown in FIG. 13, the precharge unit 13•9 is placed in proximity tothe column 13•38 of the electro-optical apparatus 13•8 in the workingchamber 13•16. This inspection apparatus is a type of apparatusirradiating an electron beam to a substrate as an inspection object,i.e. a wafer to inspect a device pattern or the like formed on the wafersurface, and therefore information of secondary electrons or the likegenerated by irradiation of the electron beam is used as information ofthe wafer surface, but the wafer surface may be charged (charge-up)depending on conditions of a wafer material, energy of irradiationelectrons and the like. Further, strongly charged sites and weaklycharged sites may appear on the wafer surface. Unevenness in chargeamount on the wafer surface causes unevenness in information ofsecondary electrons, thus making it impossible to obtain preciseinformation.

Thus, in the embodiment of FIG. 13, a precharge unit 13•9 having acharged particle irradiation unit 13•39 is provided to prevent suchunevenness. Before inspection electrons are directed to predeterminedsites of the wafer to be inspected, charged particles are irradiatedfrom the charged particle irradiation unit 13•39 of the precharge unit13•9 to eliminate charge unevenness. For the charge-up on the wafersurface, an image on the wafer surface as an inspection object is formedin advance, and the image is evaluated to perform detection, and theprecharge unit 13•9 is operated based on the detection. Furthermore, inthis precharge unit 13•9, the focus of a primary electron beam may beshifted, i.e. the beam shape may be blurred to irradiate the wafer.

FIG. 55 shows main parts of the first embodiment of the precharge unit13•9. Charged particles 55•1 are applied from a charged particleirradiation beam source 55•2 to the sample substrate W while beingaccelerated by a voltage set by a bias power supply 55•3. An inspectionsubject area 55•4 is an area already subjected to charged particleirradiation as preprocessing together with an area 55•5. An area 55•6 isone being irradiated with charged particles. In this figure, the samplesubstrate W is scanned in a direction shown by an arrow in the figure,but if the sample substrate W is scanned to and fro, another chargedparticle beam source 55•7 is placed on the opposite side of a primaryelectron beam source, and the charged particle beam sources 55•2 and55•7 are turned on and off alternately in synchronization with the scandirection of the sample substrate W as shown by a dotted line in thefigure. In this case, if energy of charged particles is too high, theyield of secondary electrons from an insulation portion of the samplesubstrate W exceeds 1, and thus the surface is positively charged, andeven if the yield is 1 or less, the phenomenon is implicated ifsecondary electrons are generated to reduce irradiation efficiency, andtherefore it is effective to set the voltage to a landing voltage of 100eV or less (ideally a voltage of 0 eV to 30 eV) at which generation ofsecondary electrons is rapidly reduced.

FIG. 56 shows the second embodiment of the precharge unit 13•9. In thisfigure, a type of irradiation beam source irradiating an electron beam56•1 as a charged particle beam is shown. The irradiation beam source iscomprised of a hot filament 56•2, an anode electrode 56•3, a shield case56•4, a filament power supply 56•5 and an anode power supply 56•6. Theanode 56•3 is provided with a slit having a thickness of 0.1 mm, a widthof 0.2 mm and a length of 1.0 mm, and the positional relation betweenthe anode 56•3 and the filament (thermal electron emission source) 56•2is a form of a three-pole electron gun. The shield case 56•4 is providedwith a slit having a width of 1 mm and a length of 2 mm, and is situatedat a distance of 1 mm from the anode 56•3, and is assembled so that theslit centers of the shield case 56•4 and the anode 56•3 match eachother. The material of the filament is tungsten (W), which iscurrent-heated at 2 A, so that an electron current of severalmicroamperes is obtained at an anode voltage of 20 V and a bias voltageof 30 V.

The example shown here is only one example and, for example, thematerial of the filament (thermal electron emission source) may be ametal having a high melting point such as Ta, Ir or Re, thoria coat W,an oxide cathode or the like, and the filament current varies dependingon the material, the line diameter and the length as a matter of course.Furthermore, other types of electron guns can be used as long asappropriate values can be set for the electron beam irradiation area,the electron current and energy.

FIG. 57 shows the third embodiment of the precharge unit 13•9. A type ofirradiation beam source irradiating ions 57•1 as a charged particle beamis shown. This irradiation beam source is comprised of a filament 57•2,a filament power supply 57•3, an emission power supply 57•4 and an anodeshield case 57•5, and an anode 57•6 and the shield case 57•5 areprovided with slits having the same size of 1 mm×2 mm, and are assembledso that the centers of both slits match each other at intervals of 1 mm.Ar gas 57•8 is introduced up to about 1 pa into the shield case 57•5through a pipe 57•7, and the shield case 57•5 is operated in an aredischarge type by the hot filament 57•2. The bias voltage is set to apositive value.

FIG. 58 shows the case of a plasma irradiation process as the fourthembodiment of the precharge unit 13•9. Its structure is the same as thatof FIG. 57. It is operated in an arc discharge type by the hot filament57•2 in the same manner as described above, but by setting the biasvoltage to 0 V, plasma 58•1 is leaked through the slit by a gas pressureand applied to the sample substrate. In the case of plasma irradiation,both positive and negative surface potentials on the surface of thesample substrate can be brought close to 0 because of the group ofparticles having both positive and negative charges compared to otherprocesses.

The charged particle irradiation unit placed in proximity to the samplesubstrate W has a structure shown in FIGS. 55 to 58. In those figures,charged particles 55•1 are irradiated under appropriate conditions sothat the surface potential is 0 for a difference in surface structure ofthe sample substrate, such as an oxide film and a nitride film and eachof sample substrates in different fabrication steps. After the samplesubstrate is irradiated under optimum irradiation conditions, i.e. thepotential of the surface of the sample substrate W is equalized orneutralized with charged particles, an image is formed with electronbeams 55•8 and 55•9 and defects are detected.

As described above, in this embodiment, deformation of a measurementimage with charge does not occur or deformation is very little if anyowing to processing just before measurement by irradiation of chargedparticles, thus making it possible to measure defects correctly.Furthermore, since the stage can be scanned by application of a largecurrent (e.g. 1 μA to 20 A, preferably 1 μA to 10 μA, more preferably 1μA to 5 μA), which has caused problems if used, a large amount ofsecondary electrons are emitted from the surface of the wafer, andtherefore a detection signal having a good S/N ratio (e.g. 2 to 1000,preferably 5 to 1000, more preferably 10 to 100) is obtained, resultingin an improvement in reliability of defect detection. Furthermore,because of the high S/N ratio, satisfactory image data can be createdeven if the stage is scanned at a higher speed, thus making it possibleto increase throughput of inspection.

FIG. 59 schematically shows an imaging apparatus comprising theprecharge unit according to this embodiment. This imaging apparatus 59•1comprises a primary optical system 59•2, a secondary optical system59•3, a detection system 59•4, and charge controlling means 59•5 forequalizing or reducing charges with which an imaging object iselectrified. The primary optical system 59•2 is an optical systemirradiating an electron beam to an inspection object W (hereinafterreferred to as object), and comprises an electron gun 59•6 emittingelectron beams, an electrostatic lens 59•8 collecting a primary electronbeam 59•7 emitted from the electron gun 59•6, a Wien filter or E×Bdeflector 59•9 deflecting the primary electron beam so that its opticalaxis is perpendicular to the surface of the object, and an electrostaticlens 59•10 collecting the electron beam. They are placed in descendingorder with the electron gun 59•6 situated at the uppermost position, andin such a manner that the optical axis of the primary electron beam 59•7emitted from the electron gun is slanted with respect to a line verticalto the surface of the object W (sample surface), as shown in FIG. 59.The E×B deflector 59•9 is comprised of an electrode 59•11 and anelectromagnet 59•12.

The secondary optical system 59•3 comprises an electrostatic lens 59•3placed on the upper side of the E×B deflector 49•9 of the primaryoptical system. The detection system 59•4 comprises a combination 59•15of a scintillator and a micro-channel plate (MCP) converting secondaryelectrons 59•14 into a light signal, a CCD 59•16 converting the lightsignal into an electric signal, and an image processing apparatus 59•17.The structure and the function of the primary optical system 59•2, thesecondary optical system 59•3 and the detection system 59•4 are the sameas those of the conventional technique, and therefore detaileddescriptions thereof are not presented.

In this embodiment, the charge controlling means 59•5 for equalizing orreducing charges with which the object is electrified comprises anelectrode 59•18 placed close to the object W between the object W andthe electrostatic lens 59•10 of the primary optical system 59•2 closestto the object W, a changeover switch 59•19 electrically connected to theelectrode 59•18, a voltage generator 59•21 electrically connected to oneterminal 59•20 of the changeover switch 59•19, and a charge detector59•23 electrically connected to the other terminal 59•22 of thechangeover switch 59•19. The charge detector 59•23 has a high impedance.The charge reducing means 59•5 further comprises a grid 59•24 placedbetween the electron gun 59•6 of the primary optical system 59•2 and theelectrostatic lens 59•8, and a voltage generator 59•25 electricallyconnected to the grid 59•24. A timing generator 59•26 indicatesoperation timing to the CCD 59•16 and image processing apparatus 59•17of the detection system 59•4, the changeover switch 59•19 of the chargereducing means 59•5, the voltage generator 59•21 and the chargedetectors 69•23 and 59•25.

The operation of the electron beam apparatus having the configurationdescribed above will now be described. The primary electron beam 59•7emitted from the electron gun 59•6 passes through the electrostatic lens59•8 of the primary optical system 59•2 to reach the E×B deflector 59•9,and is deflected so as to be perpendicular to the surface (objectsurface) WF of the object W by the E×B deflector 59•9, and applied tothe surface of the object W through the electrostatic lens 59•10. Thesecondary electrons 59•14 are emitted from the surface WF of the objectW according to properties of the object. The secondary electrons 59•14are sent through the electrostatic lens 59•13 of the secondary opticalsystem 59•3 to the combination 59•15 of a scintillator and an MCP of thedetection system 59•4, and converted into light by the scintillator, thelight is subjected to photoelectric conversion by the CCD 59•16, and theconverted electric signal causes the image processing apparatus 59•17 toform a two-dimensional image (having a gray scale). Furthermore, as inthe case of this normal type of inspection apparatus, the primaryelectron beam to be irradiated to the object can be applied to entirerequired sited on the object surface WF to collect data of the objectsurface by scanning the primary electron beam with well known deflectingmeans (not shown), or moving a table T supporting the object in thetwo-dimensional direction of X and Y, or by combination thereof.

A charge is generated near the surface of the object W with the primaryelectron beam 59•7 applied to the object W, and the object W ispositively charged. As a result, the secondary electrons 59•14 generatedfrom the surface WF of the object W have the path changed according tothe situation of the charge by the Coulomb force. As a result, the imageformed in the image processing apparatus 59•17 is deformed. The chargeof the object surface WF varied with the properties of the object W, andtherefore if the wafer is used as an object, the charge is not the sameon the same wafer, and varies with time. Thus, when patterns at twosites on the wafer are compared, defect detection may occur.

Thus, in this embodiment according to the present invention, utilizingspare time after the CCD 59•16 of the detection system 59•4 captures animage equivalent to one scan, the charge amount of the electrode 59•18placed near the object W is measured by the charge detector 59•23 havinga high impedance. A voltage for irradiating electrons appropriate to themeasured charge amount is generated by the voltage generator 59•21, thechangeover switch 59•19 is operated to connect the electrode 59•18 tothe voltage generator 59•21 after the measurement, and the voltagegenerated by the voltage generator is applied to the electrode 59•18 tooffset the charge. In this way, no deformation occurs in the imageformed in the image processing apparatus 59•17. Specifically, when ausual voltage is given to the electrode 59•18, a converged electron beamis applied to the object W, but if a different voltage is given to theelectrode 59•18, focusing conditions are significantly shifted, a largearea expected to be charged is irradiated in a small current density,and the positive charge of the positively charged object is neutralized,whereby the voltage of the large area expected to be charged can beequalized to a specific positive (negative) voltage, or the charge isequalized and reduced, whereby a lower positive (negative) voltage(including zero volt) can be achieved. The operation for offsetting thecharge is carried out for each scan.

The Wenelt electrode or mid 59•24 has a function to stop the electronbeam applied from the electron gun 59•6 in timing of spare time so thatthe measurement of the charge amount and the operation for offsettingthe charge are carried out with stability. Timing of the aboveoperation, which is indicated by the timing generator 59•26, is forexample timing shown in the timing chart of FIG. 60. Furthermore, if thewafer is used as an object, the charge amount varies depending on theposition of the wafer, and therefore a plurality of pairs of electrodes59•18, changeover switches 59•19, voltage generators 59•21 and chargedetectors 59•23 can be provided in the scanning direction of the CCD andfractionalized to perform more accurate control.

According to this embodiment, the following effects can be exhibited.

(1) Deformation of the image occurring due to charge can be reducedirrespective of the properties of the inspection object.

(2) Because charge is equalized and offset utilizing spare time inmeasurement time in the conventional process, the throughput is notaffected at all.

(3) Because processing can be carried out in real time, time forpost-processing, a memory and the like are not required.

(4) Observation of the image and detection of defects can be performedat a high speed and with high accuracy.

FIG. 61 shows the outlined configuration of a defect inspectionapparatus comprising a precharge unit according to another embodiment ofthe present invention. This defect inspection apparatus comprises theelectron gun 59•6 emitting a primary electron beam, the electrostaticlens 59•8 deflecting and shaping the emitted primary electron beam, asample chamber 61•1 capable of being evacuated by a pump (not shown), astage 61•2 situated in the sample chamber and capable of moving in ahorizontal plane with a sample such as a semiconductor wafer W placedthereon, the electrostatic lens 59•13 of a projection systemmap-projecting a secondary electron beam and/or a reflection electronbeam emitted from the wafer W by irradiation of the primary electronbeam under predetermined magnification to form an image, a detector 61•3detecting the formed image as a secondary electron image of the wafer,and a control unit 61•4 controlling the entire apparatus and detectingdefects of the wafer W based on the secondary electron image detected bythe detector 61•3. Furthermore, not only secondary electrons but alsoreflection electrons contribute to the secondary electron imagedescribed above, but the image is referred to as a secondary electronimage herein.

In the sample chamber 61•1, a UV lamp 61•5 emitting a light beam in awave range including ultraviolet light is placed above the wafer W. Theglass surface of this UV lamp 61•5 is coated with a photoelectronemission material 61•6 emitting photoelectrons e⁻ resulting from aphotoelectronic effect by the light beam emitted from the UV lamp 61•5.The UV lamp 61•5 may be any light source emitting a light beam in a waverange having a capability of emitting photoelectrons from thephotoelectron emission material 61•6. Generally, a low pressure mercurylamp emitting ultraviolet light of 254 nm is advantageous in terms of acost. Furthermore, the photoelectron emission material 61•6 may be anymaterial as long as it has a capability of emitting photoelectrons andfor example, Au or the like is preferable.

The photoelectron described above has energy different from that of theprimary electron beam, i.e. energy lower than that of the primaryelectron beam. Here, the low energy refers to the order of severalelectron volts to several tens of electron volts, preferably 0 to 10 eV.The present invention can use any means for generating electrons of suchlow energy. For example, a low energy electron gun (not shown) may beprovided in place of the UV lamp 61•5.

Further, in the case where energy of the electron gun is controlled, thedefect inspection apparatus of this embodiment comprises a power supply61•7. The negative pole of this power supply 61•7 is connected to thephotoelectron emission material 61•6, and the positive pole is connectedto the stage 61•2. Thus, the photoelectron emission material 61•6 has anegative voltage applied thereto with respect to the voltage of thestage 61•2 and the wafer W. Energy of the low energy electron beam canbe controlled with the predetermined voltage.

The detector 61•3 may have any configuration as long as the secondaryelectron image formed by the electrostatic lens 59•13 can be convenedinto a signal capable of being subjected to post-processing. Forexample, as shown in FIG. 62 in detail, the detector 61•3 may comprise amicro-channel plate (MCP) 62•1, a fluorescent screen 62•2, a relayoptical system 62•3, and an imaging sensor 62•4 constituted by a largenumber of CCD elements. The micro-channel plate 62•1 has a large numberof channels in a plate, and further generates a large number ofelectrons while secondary electrons or reflection electrons made to forman image by the electrostatic lens 59•13 pass through the channels. Thatis, it amplified secondary electrons. The fluorescent screen 62•2converts secondary electrons into light by emitting fluorescence byamplified secondary electrons. The relay lens 62•3 guides thefluorescence to the CCD imaging sensor 62•4, and the CCD imaging sensor62•4 converts the intensity distribution of secondary electrons on thesurface of the wafer W into an electric signal or digital image data foreach element and outputs the same to the control unit 61•4.

The control unit 61•4 may be constituted by a general personal computer61•8. The computer 61•8 comprises a control unit main body 61•9performing various kinds of control and computation processing accordingto a predetermined program, a CRT 61•10 displaying the result ofprocessing by the main body, and an input unit 61•11 such as a keyboardand a mouse for an operator to input commands. Of course, the controlunit 61•4 may be constituted by hardware dedicated to defect inspectionapparatus, a workstation or the like.

The control unit main body 61•9 is comprised of a CPU, a RAM, a ROM, ahard disk and various kinds of control boards such as a video board (notshown). A secondary electron image storage area for storing electricsignals received from the detector 61•3, i.e. digital image data ofsecondary electron images of the wafer W is assigned on a memory of aRAM, hard disk or the like. Furthermore, a defect detection program61•13 for reading secondary electron image data from a storage area61•12, and automatically detecting defects of the wafer W according to apredetermined algorithm based on the image data is stored on the harddisk in addition to a control program for controlling the entire defectinspection apparatus. For example, the defect inspection program 61•13has a function to compare the inspection site of the wafer W to anotherinspection site, and report a pattern different from patterns of mostother sites to the operator as defects and display the pattern, forexample. Further, a secondary electron image 61•14 may be displayed on adisplay unit of the CRT 61•10 to detect defects of the wafer W by visualobservation of the operator.

The action of the electron beam apparatus according to the embodimentshown in FIG. 61 will now be described using the flowchart of FIG. 63 asan example. First, the wafer W to be inspected is set on the stage 61•2(step 63•1). In this case, a large number of wafers W stored in a loader(not shown) may be automatically set on the stage 61•2 on a one-by-onebasis. Then, a primary electron beam is emitted from the electron gun59•6, and applied to a predetermined inspection area on the surface ofthe set wafer W through the electrostatic leas 59•8 (step 63•2).Secondary electrons and/or reflection electrons (hereinafter referred toonly as “secondary electrons”) are emitted from the wafer W irradiatedwith the primary electron beam and as a result, the wafer W is chargedup to a positive potential.

Then, a generated secondary electron beam is made to form an image onthe detector 61•3 under a predetermined magnification by theelectrostatic lens 59•13 in an enlarged projection system (step S63•3).At this time, the UV lamp 61•5 is made to emit light with a negativevoltage applied to a photoelectron emission material 65•1 with respectto the stage 61•2 (step 63•4). As a result, ultraviolet light with thefrequency of ν emitted from the UV lamp 61•5 causes photoelectrons to beemitted from the photoelectron emission material 65•1 with its energyquantum of hν (h represents Planck constant). The photoelectrons e⁻ areapplied from the negatively charged photoelectron emission material 61•6to the wafer W positively charged up to electrically neutralize thewafer W. In this way, the secondary electron beam is made to form animage on the detector 61•3 without being substantially influenced by thepositive potential of the wafer W.

The image of the secondary electron beam (having alleviated imagefaults) emitted from the wafer W electrically neutralized in this way isdetected by the detector 61•3, and converted into digital image data,and the image data is outputted (step 63•5). Then, the control unit 61•4carries out processing for detection of defects of the wafer W based onthe detected image data according to the defect detection program 61•13(step 63•6). In this defect detection processing, the control unit 61•4extracts a defective portion by comparing detection images of detecteddies as described previously if the wafer has a large number of the samedies. A reference secondary electron image of the wafer having nodefects, previously stored in the memory, may be compared with anactually detected secondary electron image to automatically detect adefective portion. At this time, the detection image may be displayed onthe CRT 61•10, and a portion judged as a defective portion may marked,whereby the operator can finally check and determine whether the wafer Wactually has defects or not. A specific example of this defect detectionprocess will be further described later.

If it is determined that the wafer W has defects as a result of thedefect detection processing of step 63•5 (positive determination in step63•7), the operator is warmed of existence of defects (step 63•8). As amethod of warning, for example, a message indicating existence ofdefects may be displayed on the display unit of the CRT 61•10, and atthe same time, an enlarged image 61•14 of a pattern having defects maybe displayed. The defective wafer may be immediately taken from thesample chamber 61•1, and stored in a storage site different from a sitefor wafers having no defects (step 63•9).

As a result of the defect detection processing in step 63•6, whether anyarea to be inspected still exists or not is determined for the wafer Was a current inspection object (step 63•10) if it is determined that thewafer W has no defects (negative determination in step 63•7). If an areato be inspected still exists (positive determination in step 63•10), thestage 61•2 is driven to move the wafer W so that other area to beinspected next is within the area irradiated with the primary electronbeam (step 63•11). Then, processing returns to step 63•2, where the sameprocessing is repeated for the other inspection area.

If no area to be inspected exists (negative determination in step63•10), or after the step of taking the wafer (step 63•9), whether thewafer W as a current inspection object is the last wafer or not i.e.whether or not any that has not been inspected yet exists on a loader(not shown) is determined (step 63•12). If the wafer in not the lastwafer (negative determination in step 63•12), the inspected wafer isstored in a predetermined place, and instead a new wafer that has notbeen inspected yet is set on the stage 61•2 (step 63•13). Then,processing returns to step 63•2, where the same processing is repeatedfor the wafer. If the wafer is the last wafer (positive determination instep 63•12), the inspected wafer is stores in a predetermined storageplace to complete all steps. The identification numbers of cassettes,the identification numbers of wafers, for example, the lot numbers arestored for management.

Irradiation of UV photoelectrons (step 63•4) can be carried out in anytiming and within any time period as long as the secondary electronimage can be detected (step 63•5) in a state in which positive charge-upof the wafer is avoided, and image faults are reduced. The UV lamp 61•5may be lit all the time while processing of FIG. 63 is continued, butthe UV lamp 61•5 may be lit and unlit periodically with the time perioddefined for each wafer. In the latter case, as timing of light emission,light emission may be started before the secondary electron beam is madeto form an image (step 63•3) and before the primary electron beam isapplied (step 63•2), other than the timing shown in FIG. 63. Irradiationof UV photoelectrons is preferably continued at least during detectionof secondary electrons, but the irradiation of UV photoelectrons may bestopped even before or during detection of the secondary electron imageif the wafer is electrically neutralized sufficiently.

Specific examples of the defect detection process at step 63•6 are shownin FIGS. 64( a) to (c). First, in FIG. 64( a), an image 64•1 of a diedetected first and an image 64•2 of another die detected second areshown. If it is determined that an image of another die detected thirdis identical or similar to the first image 64•1, it is determined thatan area 64•3 of the second die image 64•2 has defects, and thus thedefective area can be detected.

An example of measurement of a line width of a pattern formed on thewafer is shown in FIG. 64( b). Reference numeral 64•6 denotes anintensity signal of actual secondary electrons when an actual pattern64•4 on the wafer is scanned in a direction 64•5, and a width 64•8 of anarea where this signal continuously exceeds a threshold level 64•7defined by correction in advance can be measured as the line width ofthe pattern 64•4. If the line width measured in this way is not within apredetermined range, it can be determined that the pattern has defects.

An example of measurement of a potential contrast of a pattern formed onthe wafer is shown in FIG. 64( c). In the configuration shown in FIG.61, an axis-symmetric electrode 64•9 is provided above the wafer W andfor example, a potential of −10 V is given with respect to the waferpotential of 0 V. A equipotential surface of −2 V at this time has ashape denoted by reference numeral 64•10. Here, patterns 64•11 and 64•12formed on the wafer have potentials of −4 V and 0 V, respectively. Inthis case, secondary electrons emitted from the pattern 64•11 have aupward velocity equivalent to kinetic energy of 2 eV at the −2 Vequipotential surface 64•10, and therefore the secondary electrons jumpover the potential barrier 64•10, escape from the electrode 64•9 asshown in an orbit 64•13, and are detected by the detector 61•3. On theother hand, secondary electrons emitted from the pattern 64•12 cannotjump over the −2 V potential barrier, and is returned back to the wafersurface as shown in an orbit 64•14, and therefore the secondaryelectrons are not detected. Thus, the detection image of the pattern64•11 is bright, while the detection image of the pattern 64•12 is dark.In this way, the potential contrast is obtained. If the brightness ofthe detection image and the potential are corrected in advance, thepotential of the pattern can be measured from the detection image. Thedefective area of the pattern can be evaluated from the potentialdistribution.

Furthermore, if there is an area floating in the die, an electric chargecan be added by the precharge unit to charge the floating area andestablish electrical connection to produce a potential differencebetween the area and a grounded area. Potential contrast data in thisstate can be acquired and analyzed to identify the floating area. It canbe used as a defect identification process when killer defects and thelike exist. The potential contrast data may be converted into apotential contrast image to compare the potential contrast image with apotential contrast image of a pattern of another die, or compare thepotential contrast image with a potential contrast image acquired fromdesign data of the CAD or the like.

FIG. 65 shows the outlined configuration of a defect inspectionapparatus comprising a precharge unit according to another embodiment ofthe present invention. Furthermore, components the same as those of theembodiment of FIG. 61 are given like symbols, and detailed descriptionsthereof are not presented. In this embodiment, as shown in FIG. 65, theglass surface of the UV lamp 61•5 is not coated with the photoelectronemission material. Instead, a photoelectron emission plate 65•1 isplaced above the wafer W in the sample chamber 61•1, and the UV lamp61•5 is placed at a position such that emitted ultraviolet light isapplied to the photoelectron emission plate 65•1. The negative pole of apower supply 71•7 is connected to the photoelectron emission plate 65•1,and the positive pole of the power supply is connected to the stage61•2. The photoelectron emission plate 65•1 is made of metal such as Au,or may be a plate coated with such a metal.

The action of the embodiment of FIG. 65 is the same as that of theembodiment of FIG. 61. In the embodiment of FIG. 65, photoelectrons canbe applied to the surface of the wafer W as appropriate, and thus aneffect the same as that of the embodiment of FIG. 61 is exhibited.

FIG. 66 shows the outlined configuration of a defect inspectionapparatus comprising a precharge unit according to still anotherembodiment of the present invention. Furthermore, components identicalto those of the embodiments of FIGS. 61 and 65 are given like symbols,and detailed descriptions thereof are not presented. In the embodimentof FIG. 66, as shown in this figure, a transparent window material 66•1is provided on the side wall of the sample chamber 61•1, and the UV lamp61•5 is placed outside the sample chamber 61•2 so that ultraviolet lightemitted from the UV lamp 61•5 is applied through the window material66•1 to the photoelectron emission plate 65•1 placed above the wafer Win the sample chamber 61•1. In the embodiment of FIG. 66, the UV lamp61•5 is placed outside the sample chamber 61•1 to be evacuated, andtherefore necessity to consider an anti-vacuum performance of the UVlamp 61•5 is eliminated, thus making it possible to widen a choice ofoptions of the UV lamp 61•5 compared to the embodiments of FIGS. 61 and65.

Other actions of the embodiment of FIG. 66 are the same as those of theembodiments of FIGS. 61 and 65. In the embodiment of FIG. 66,photoelectrons can be applied to the surface of the wafer W asappropriate, and therefore an effect the same as those of theembodiments of FIGS. 61 and 65 is exhibited.

The embodiments have been described above, but the defect inspectionapparatus comprising the precharge unit according to the presentinvention is not limited to the examples described above, but may bechanged as appropriate within the spirit of the present invention. Forexample, the semiconductor wafer W is used as a sample to be inspected,but the sample to be inspected of the present invention is not limitedthereto, and any type allowing defects to be detected with an electronbeam can be selected. For example, a mask having a pattern for exposureof the wafer to light, a transparent mask (stencil mask) or the like maybe dealt with as an inspection object. Furthermore, the apparatus may beused not only for the semiconductor process but also for inspection andevaluation related to micro-machines and liquid crystals as a matter ofcourse.

Furthermore, as the electron beam apparatus for inspection of defects,the configuration of FIGS. 61 to 66 is shown, but the electro-opticalsystem and the like may changed as appropriate. For example, theelectron beam irradiating means (59•6 and 59•8) of the defect inspectionapparatus shown in the figure makes the primary electron beam enter thesurface of the wafer W aslant from the above, but means for deflectingthe primary electron beam may be provided below the electrostatic lens59•13 to make the primary electron beam enter the surface of the wafer Wat a right angle. Such deflecting means includes, for example, a Wienfilter deflecting the primary electron beam with a field E×B in whichthe electric field is orthogonal to the magnetic field.

Further, as means for emitting photoelectrons, any means may be employedas a matter of course other than the combination of the UV lamp 61•5 andthe photoelectron emission member 61•6 or photoelectron emission plate65•1 shown in FIGS. 61 to 66.

The flow of the flowchart of FIG. 63 is not limited thereto. Forexample, for a sample judged as being defective at step 63•7, inspectionof defects for other areas is not carried out, but the flow of theprocess may be changed so that detection of defects is carried out overall the areas. Furthermore, if the area to be irradiated with theprimary electron beam is enlarged so that one irradiation can cover allthe inspection area of the sample, steps 63•10 and 6•11 may be omitted.

Further, in FIG. 63, if it is determined that the wafer has defects atstep 63•7, the operator is immediately warned of existence of defects atstep 63•8 and post-processing is carried out (step 63•9), but the flowmay be changed so that defect information is recorded, and after batchprocessing is completed (after positive determination in step 63•12),defect information of the defective wafer is reported.

As described in detail above, according to the defect inspectionapparatus and the defect inspection process according to the embodimentsof FIGS. 61 and 66, electrons having energy different from that of theprimary electron beam, i.e. energy lower than that of the primaryelectron beam is supplied to the sample, and therefore an excellenteffect is obtained such that the positive charge-up on the samplesurface associated with emission of secondary electrons is reduced, andhence image faults of the secondary electron beam associated with thecharge-up can be eliminated, thus making it possible to inspect defectsof the sample with high accuracy.

Further, if the defect inspection apparatus of FIGS. 61 and 66 is usedfor the device production process, an excellent effect is obtained suchthat the yield of products can be improved and defective products can beprevented from being dispatched, because defect inspection for thesample is carried out using the defect inspection apparatus describedabove.

The case has been described above where the electron beam is softlyapplied to the sample surface in low energy such that electron energyfor precharge is mainly 100 eV or less, but an image may be acquired inthe positive charge or negative charge mode or the reflection electronmode after performing precharge at 2 kV to 20 kV, preferably 3 to 10 kV,more preferably 3 to 5 kV. In the negative charge mode, precharge may beperformed in energy the same as lauding energy of the electron beamduring inspection.

Furthermore, it is effective to coat the sample surface with aconductive thin film for control of charge. The suitable thickness inthis case is 1 to 100 mm, preferably 1 to 10 nm, more preferably 1 to 3nm. Further, if the image is acquired after the sample surface iscleaned by sputter etching or the like, a cleaner image is obtained.Coating of the conductive thin film and sputter etching may be usedalone, or in combination with precharge. For example, precharge may beperformed to acquire an image after sputter etching, or precharge may beperformed after coating of the conductive thin film after sputteretching.

2-5) Vacuum Pumping System

A vacuum pumping system is comprised of a vacuum pump, a vacuum valve, avacuum gage, vacuum piping and the like and an electro-optical system, adetection unit, a sample chamber and a load lock chamber are evacuatedaccording to a predetermined sequence. In each unit, the vacuum valve iscontrolled so as to achieve a required degree of vacuum. The degree ofvacuum is monitored all the time, and if an abnormality occurs,emergency control of an isolation valve and the like is performed withan interlock feature to ensure the degree of vacuum. For the vacuumpump, a turbo-molecular pump is used for main pumping and a roots-typedry pump is used for rough pumping. The practical pressure of theinspection site (electron beam irradiation area) is 10⁻³ to 10⁻⁵ Pa,preferably 10⁻⁴ to 10⁻⁶ Pa lower by one order.

2-6) Control System

A control system is mainly comprised of a main controller, a controllingcontroller and a stage controller. The main controller is provided witha man-machine interface, through which the operation by the operator iscarried out (various kinds of instructions/command, input of recipes andthe like, instruction to start inspection, switching between theautomatic mode and the manual mode, input of all required commandsduring the manual inspection mode, and the like). In addition,communication with a host computer at a factory, control of the vacuumpumping system, transportation of a sample such as a wafer, control ofalignment, transmission of commands to the other controlling controllerand stage controller, reception of information and the like are carriedout through the main controller. Furthermore, the controller comprises afunction to acquire image signals from an optical microscope, a stagevibration correction function to make the electro-optical systemfeedback a stage variation signal to correct deterioration of the image,and an automatic focus correction function to detect a displacement ofthe sample observation position in the Z direction (axial direction ofthe secondary optical system), feedback the displacement to theelectro-optical system, and automatically correct the focus. Exchange offeedback signals and the like with the electro-optical system, andexchange of signals from the stage are performed through the controllingcontroller and the stage controller, respectively.

The controlling controller is engaged in mainly control of an electronbeam optical system (control of electron gun, lens, aligner, highaccuracy power supply for Wien filter and the like). Specifically,control is performed so that a constant electron current is alwaysapplied to the irradiation area even when the magnification is changed,and control for automatic voltage setting for each lens system and thealigner matching each operation mode, and the like (interlock control),such as automatic voltage setting for each lens system and the alignermatching each magnification, is performed.

The stage controller mainly performs control relating to movement of thestage to allow precise movement in X and Y directions in the order ofinn (with errors within about ±5 μm or smaller, preferably ±1 μm orsmaller, more preferably ±0.5 μm or smaller). Furthermore, in thisstage, control in the rotational direction (θ control) is performed witherrors within about ±10 seconds, preferably ±1 second, more preferably±0.3 seconds). The configuration of the control system will bespecifically described below.

2-6-1) Configuration and Function

This apparatus provides a function to image a specified position in awafer with an election microscope or optical microscope and display thesame, a function to image the specified position in the wafer with theelectron microscope to detect and classify defects, and a function toimage the position at which defects are detected with the electronmicroscope or optical microscope and display the same. Furthermore, forachievement and maintenance of the above functions, the apparatus has anelectro-optical system control function, a vacuum system controlfunction, a wafer transportation control function, a single componentoperation function, an imaging function, an automatic defect inspectionprocessing function, an apparatus abnormality detection function, and anapparatus start/stop processing function.

Auxiliary functions are listed below.

(1) Electro-optical system control function

(a) Lens voltage application control

-   -   (a-1) Interlock control    -   (a-2) Voltage application with application function    -   (a-3) Multipole lens interlock voltage application    -   (a-4) Wobble control

(b) Electron beam output adjustment

-   -   (b-1) Preheat (Gum)    -   (b-2) Heat up (Gun)    -   (b-3) Emission current control (Bias control)        (2) Vacuum system control function

(a) Individual chamber evacuation/N, vent

(b) Specified chamber batch evacuation/N₂ vent

(3) Wafer transportation control function

Step operation/full automatic operation of following operations

(a) Wafer load

(b) Wafer unload

(4) Single component operation function

(5) Imaging function

A selection is made from the following two input lines and an image isformed.

(a) CCD camera

-   -   Optical microscope low power (pixel size: 2.75 μm/pix)    -   Optical microscope high power (pixel size: 0.25 μm/pix)

(b) TDI camera

(b-1) TDI-still

(b-2) TDI-scan

EB×80 (pixel size: 0.2 μm/pix)

EB×160 (pixel size: 0.1 μm/pix)

EB×320 (pixel size: 0.05 μm/pix)

EB×480 (pixel size: 0.03 μm/pix).

Further, a user mode designation function is provided as a function tolimit operational items according to the skill/knowledge level of theoperator for prevention of an accident resulting from an erroneousoperation. This user mode is designated as a user ID and a passwordinputted when a GUI (graphical user interface) is started.

The user mode includes a maintenance mode, a recipe creation mode, andan operator mode, the operation is carried out in the maintenance modeduring setup work after installation of the apparatus and maintenancework, necessary operations and procedures are supported in the recipecreation mode during creation of a recipe, and inspection is performedusing the created recipe in the operator mode during automatic defectinspection. The relation between each user mode and the apparatusoperation form is shown in FIG. 67.

Maintenance mode . . . single component operation, wafer transportation,vacuum system control, electro-optical system control, observation(optical microscope imaging, TDI imaging), defect inspection, review

Recipe creation mode . . . wafer transportation, observation (opticalmicroscope imaging, TDI imaging), defect inspection, review

Operator mode . . . automatic defect inspection (automatic control ofnecessary functions such as wafer transportation), review.

This apparatus has an apparatus constant and a recipe as variableparameters required for the operation. The apparatus constant isspecified as a parameter for absorbing apparatus specific errors (suchas a mounting error), and the recipe is specified as a parameter forspecifying various kinds of conditions to automatically perform defectinspection. The apparatus constant is set during setup work and aftermaintenance work, and is essentially unchanged thereafter.

The recipe is classified into a transportation recipe, an alignmentrecipe, a die map recipe, a focus map recipe and an inspection recipe,defect inspection is performed according to these recipes, setting workis therefore carried out before inspection processing is performed, anda plurality of patterns of settings are stored.

For the procedure during recipe creation, the wafer is conveyed onto thestage (wafer is loaded) as a first step as shown in FIG. 68. After awafer cassette is installed in the apparatus, wafer search is carriedout to detect existence/nonexistence of the wafer in each slot in thecassette, a wafer size, a notch/ori-fla type, and a notch direction(when loaded onto the stage) are designated for the detected wafer, andthe wafer is loaded according to the procedure shown in FIGS. 69 and 70.These conditions are stored in the transportation recipe. The directionof placement of the die of the wafer loaded onto the stage does notnecessarily match the scan direction of the TDI camera (FIG. 71). Inorder that the directions match each other, an operation for rotatingthe wafer on a θ stage is required, and this operation is calledalignment (FIG. 72). Alignment practice conditions after the wafer isloaded onto the stage are stored in the alignment recipe.

Furthermore, a die map (FIG. 73) showing the arrangement of dies duringalignment is created, the die size, the position of the origin die(starting point showing the position of the die) and the like are storedin the die map recipe.

2-6-2) Alignment Procedure

For the alignment (positioning) procedure, rough positioning isperformed with a low power of an optical microscope, then positioning isperformed with a high power of the optical microscope, and finally finepositioning is performed with an EB image.

A. Imaging with Optical Microscope Low Power

(1) <First, Second and Third Search Die Designation and TemplateDesignation>

(1-1) First search die designation and template designation

The stage is moved by a user operation so that the lower left corner ofthe die positioned below the wafer is positioned near the center of acamera, the position is determined, and then a template image forpattern matching is acquired. This die is a die serving as a referencefor positioning, and the coordinates of the lower left corner arecoordinates of a feature point. Hereinafter, pattern matching isperformed with this template image, whereby correct positionalcoordinates of any die on the substrate are measured. For this templateimage, an image forming a unique pattern in the search area must beselected.

Furthermore, in this example, the lower left corner is a template imageacquirement position for pattern matching, but the position is notlimited thereto, and any position in the die may be selected as afeature point. Generally, however, since coordinates can be identifiedmore easily for the corners than for points in the die and on the edgeof the die, any one of the four corners is preferably selected.Similarly, in this example, the template image for pattern matching isacquired for the die positioned below the wafer but as a matter ofcourse, any die may be selected such that alignment can more easily beperformed.

(1-2) Second search die designation

The die at the immediate right of the search die is designated as asecond search die, the stage is moved by a user operation so that thelower left corner of the second search die is positioned near the centerof the camera, the position is determined, and then the template imageacquired in the procedure (1-1) is used to automatically perform patternmatching, whereby accurate coordinate values of the second search diematching the template image designated with the first search die isacquired.

Furthermore, in this example, the die at the immediate right of thefirst search die is the second search die, but the second search die ofthe present invention is not limited thereto, as a matter of course. Itis essential that a point should be selected which makes it possible tocorrectly know by pattern matching a positional relation of dies in theline direction from the reference point with which the positionalcoordinates of the correct feature point are known. Thus, for example,the die at the immediate left of the first search die can be designatedas the second search die.

(1-3) Third search die designation

The die just above the second search die is designated as a third die,the stage is moved by a user operation so that the lower left corner ofthe third search die is positioned near the center of the camera, theposition is determined, and then the template image acquired in theprocedure (1-1) is used to automatically perform pattern matching,whereby accurate coordinate values of the third search die matching thetemplate image designated with the first search die is acquired.

Furthermore, in this example, the die just above the second search dieis the third search die, but the third search die of the presentinvention is not limited thereto, as a matter of course. It is essentialthat a positional relation including distances of the coordinates of thefeature point of dies in the row direction can be known using, as areference, the die with which the correct coordinates of the featurepoint are known. Thus, the die just above the first search die can besuitably used as an alternate.

(2) <Optical Microscope Low Power Y Direction Pattern Matching>

(2-1) The amount of movement to the pattern of the upper neighboring dieis calculated from the relation between the pattern match coordinates(X2, Y2) of the second search die and the pattern match coordinates (X3,Y3) of the third search die.dX=X3−X2dY=Y3−Y2

(2-2) Using the calculated amount of movement (dX, dY), the stage ismoved to the coordinates (XN, YN) at which the pattern just above thefirst search die exists (is expected to exist).XN=X1+dXYN=Y1+dY

* (X1, Y1): coordinates of pattern of first search die

(2-3) After movement of the stage, imaging is performed with an opticalmicroscope low magnification, the template image is used to carry outpattern matching to acquire the accurate coordinate values (XN, YN) ofthe pattern that is currently observed, and 1 is set as an initial valueof a number of detected dies (DN).

(2-4) The amount of movement (dX, dY) from the pattern coordinates (X1,Y1) of the first search die to the coordinates (XN, YN) of the patternthat is currently imaged is calculated.dX=XN−X1dY=YN−Y1

(2-5) The stage is moved in an amount of movement (2*dX, 2*dY) twice aslarge as the calculated amount of movement (dX, dY) with the firstsearch die as a starting point.

(2-6) After movement of the stage, imaging is performed with an opticalmicroscope low magnification, the template image is used to carry outpattern matching to update the accurate coordinate values (XN, YN) ofthe pattern that is currently observed, and the number of detected diesis increased by a factor of 2. See FIG. 74 for this procedure.

(2-7) The procedures (2-4) to (2-6) are repeatedly carried out towardthe upper part of the wafer until a predesignated Y coordinate value isexceeded.

Furthermore, in this example, to improve accuracy, to reduce the numberof processes (number of repetitions) and to reduce processing time,movement is repeated in a twofold amount of movement. If there is noproblem with accuracy, and further reduction in processing time isdesired, movement may be carried out in a high integral multiple amountgreater than twofold amount, such as a three-fold or four-fold amount.For further improvement in accuracy, movement may be repeated in a fixedamount of movement. Any of these cases is incorporated in the number ofdetected dies as a matter of course.

(3) <Optical Microscope Low Magnification θ Rotation>

(3-1) Using the amount of movement from the pattern coordinates (X1, Y1)of the first search die to the accurate coordinate values (XN, YN) ofthe pattern of the die searched lastly, and the number of dies (DN)detected in the meantime, an amount of rotation (θ) and a die size inthe Y direction (YD) are calculated (see FIG. 75).dX=XN−X1dY=YN−Y1θ=tan⁻¹(dX/dY)YD=sqrt((dX)²+(dY)²)DN*sqrt(A)=(A)^(1/2)

(3-2) The stage is rotated to θ in the calculated amount of rotation(θ).

B. Imaging with Optical Microscope High Magnification

(1) A procedure the same as the procedure (1) for the optical microscopelow magnification is carried out using an optical microscope highmagnification image.

(2) A procedure the same as the procedure (2) for the optical microscopelow magnification is carried out using an optical microscope highmagnification image.

(3) A procedure the same as the procedure for the optical microscope lowmagnification is carried out.

(4) <Check of Allowable Value after Optical Microscope High Power θRotation>

(4-1) “First search die, designation of template of optical microscopehigh magnification”

The coordinates (X′1, Y′1) of the first search die after rotation arecalculated from the coordinated (X1, Y1) before rotation and the amountof rotation (θ), the stage is moved to the coordinates (X′1, Y′1), theposition is determined, and then a template image for pattern matchingis acquired.X′1=x ₁*cos θ−y ₁*sin θY′1=x ₁*sin θ+y ₁*cos θ

(4-2) Optical microscope high magnification Y direction pattern matching

The stage is moved in the Y direction by dY from the coordinates (X′1,Y′1) of the first search die after rotation, and pattern matching iscarried out to acquire the accurate coordinate values (XN, YN) of thepattern that is currently observed.

(4-3) An amount of movement (dX, dY) from the coordinates (X′1, Y′1) ofthe first search die after rotation to the coordinates (XN, YN) of thepattern that is currently imaged is calculated.dX=XN−X′1dY=YN−Y′1

(4-4) The stage is moved in an amount of movement (2*dX, 2*dY) twice aslarge as the calculated amount of movement (dX, dY) with the firstsearch die as a starting point.

(4-5) After movement of the stage, imaging is performed with an opticalmicroscope high magnification, and the template image is used to carryout pattern matching to update the accurate coordinate values (XN, YN)of the pattern that is currently observed.

(4-6) The procedures (4-3) to (4-5) are repeatedly carried out towardthe upper part of the wafer until a predesignated Y coordinate value isexceeded.

(4-7) Calculation of rotation of θ

Using the amount of movement from the coordinates (X′1, Y′1) of thefirst search die after rotation to the accurate coordinate values (XN,YN) of the pattern of the die searched lastly, an amount of rotation (θ)is calculated.dX=XN−X1dY=YN−Y1θ=tan⁻¹(dX/dY)

(4-8) Check of optical microscope high magnification θ allowable value

Whether the amount of rotation (θ) calculated in the procedure (4-7)equals a predefined value or smaller is checked. If the amount ofrotation (θ) is greater than the predefined value, the calculated amountof rotation (θ) is used to rotate the stage to θ, and then theprocedures (4-1) to (4-8) are carried out again. However, in case wherethe amount of rotation (θ) is not within an allowable range even if theprocedures (4-1) to (4-8) are carried out a specified number of times,the operation is considered as an error and processing is stopped.

C. Alignment with EB Image

(1) <Y search first die, designation of template of EB>

A procedure the same as the procedure (1) for the optical microscopehigh magnification is carried out using an EB image.

(2) <EB: Y direction pattern matching>

A procedure the same as the procedure (2) for the optical microscopehigh magnification is carried out using an EB image.

(3) <EB: θ rotation>

A procedure the same as the procedure (3) for the optical microscopehigh magnification is carried out using an EB image.

(4) <EB: check of allowable value after θ rotation>

A procedure the same as the procedure (4) for the optical microscopehigh magnification is carried out using an EB image.

(5) The procedures (1) to (4) are carried out using an EB image of ahigh magnification as required.

(6) An appropriate value of an X direction die size (XD) is calculatedfrom the coordinates (X1, Y1) of the first search die and thecoordinates (X2, Y2) of the second search die.dX=X2−X1dY=Y2−Y1XD=sqrt((dX)²+(dY)²)*sqrt(A)=√AD. Creation of Die Map Recipe(1) <X search first die, designation of template of EB>

The stage is moved by a user operation so that the lower left corner ofthe die positioned at the left end of the wafer is positioned near thecenter of a TDI camera, the position is determined, and then a templateimage for pattern matching is acquired. For this template image, animage forming a unique pattern in the search area must be selected.

(2) <EB: X Direction Pattern Matching>

(2-1) The approximate value of the X direction die size (XD) is used tomove the stage to coordinates (X1+XD, Y1) at which the pattern of thedie at the immediate right of the X search first die exists (is expectedto exist).

(2-2) After movement of the stage, an EB image is formed by the TDIcamera, the template image is used to perform pattern matching toacquire the accurate coordinates (XN, YN) of the pattern that iscurrently observed, and 1 is set as an initial value of the number ofdetected dies (DN).

(2-3) An amount of movement (dX, dY) from the pattern coordinates of theX search first die to the coordinates (XN, YN) of the pattern that iscurrently observed.dX=XN−X1dY=YN−Y1

(2-4) The stage is moved in an amount of movement (2*dX, 2*dY) twice aslarge as the calculated amount of movement (dX, dY) with the X searchfirst die as a starting point.

(2-5) After movement of the stage, an EB image is formed by the TDIcamera, the template image is used to perform pattern matching to updatethe accurate coordinates (XN, YN) of the pattern that is currentlyobserved, and the number of detected dies is increased by a factor of 2.

(2-6) The procedures (2-3) to (2-5) are repeatedly carried out in theright direction of the wafer until a predesignated X coordinate value isexceeded.

(3) <Calculation of X Direction Gradient>

A stage movement direct error (Φ) and an X direction die size (XD) arecalculated using the amount of movement from the pattern coordinates(X1, Y1) of the X search first die to the accurate coordinate values(XN, YN) of the pattern of the die searched lastly, and the number ofdies (DN) detected in the meantime.dX=XN−X1dY=YN−Y1Φ=tan⁻¹(dX/dY)XD=sqrt((dX)²+(dY)²)DN*sqrt(A)=√A(4) <Creation of Die Map>

In this way, the X direction die size (XD) is determined, and it iscombined with the Y direction die size (YD) previously determined whenthe amount of rotation (θ) is calculated to create a die map(information of an ideal arrangement of dies). From the die map, anideal arrangement of dies is known. On the other hand, actual dies onthe substrate are influenced by, for example, mechanical errors of thestage (errors of parts such as a guide, and assembly), errors of aninterferometer (e.g. due to problems of assembly of a mirror or thelike), and deformation of the image due to charge-up, and may not benecessarily observed as an ideal arrangement, but the error between theposition of the actual dies and the ideal arrangement on the die map isknown, and this error is considered and automatically corrected whileinspection is carried out.

E. Procedure for Creation of Focus Recipe

A procedure for creation of a focus recipe will now be described. Thefocus recipe stores information of an optimum focus position at anyposition on the surface of a sample such as a substrate, or variousconditions about the focus position in a predetermined format such as atable. In a focus map recipe, focus conditions are set only fordesignated positions on the wafer, and focus values between designatedpositions are linearly interpolated (see FIG. 76). The procedure forcreation of a focus recipe is as follows.

(1) Focus measurement object dies are selected from the die map.

(2) Focus measurement points in the die are set.

(3) The stage is moved to each measurement point, and a focus value(CL12 voltage) is manually adjusted based on an image and a contrastvalue.

The die map created by alignment processing provides ideal positioninformation calculated from die coordinates at the both ends of thewafer, and an error occurs between the die position on the die map andthe actual die position due to various factors (see FIG. 77). Aprocedure for creating parameters for absorbing the error is called finealignment, and information of the error between the die map (ideal dieposition information) and the actual die position is stored in a finealignment recipe. The information set here is used during defectinspection. In the fine alignment recipe, errors are measured only fordies designated on the die map, and errors between designated dies arelineally interpolated.

F. Fine Alignment Procedure

(1) Error measurement object dies for fine alignment are designated fromthe die map.

(2) A reference die is selected from the error measurement object dies,and the position of the reference die is defined as a point where theerror with the die map is zero.

(3) The lower left corner of the reference die is imaged by the TDIcamera to acquire a template image for pattern matching.

* A unique pattern in the search area is selected as a template image.

(4) Coordinates (X0, Y0) (on the die map) at the lower left of theneighboring error measurement object die is acquired, and the stage ismoved. After movement of the stage, imaging is performed by the TDIcamera, and pattern matching is carried out using the template image ofthe procedure (3) to acquire accurate coordinate values (X, Y).(5) Error between the coordinate values (X, Y) acquired by patternmatching and coordinate values (X0, Y0) on the die map are stored.(6) The procedures (4) and (5) are carried out for all the errormeasurement object dies.2-6-3) Defect Inspection

For defect inspection, as shown in FIG. 78, conditions of theelectro-optical system are set (imaging magnification and the like areset), the stage is moved while irradiating an electron beam to performTDI scan imaging (FIG. 79), and defect inspection is carried out in realtime by an inspection dedicated processing unit (IPE) according to theset inspection conditions (array inspection conditions, randominspection conditions, inspection areas).

In an inspection recipe, conditions of the electro-optical system,inspection object dies, inspection areas, the inspection process(random/array) and the like are set (A and B of FIG. 80).

Furthermore, to acquire stable images for defect inspection, EOcorrection for inhibiting blurting of formed images resulting frompositional deviations and speed unevenness, die position correction forabsorbing errors between the ideal arrangement on the die map and theactual die position, and focus adjustment for interpolating focus valuesof the entire wafer area using focus values previously measured atfinite measurement points are simultaneously carried out in real time.

In the scan operation of defect inspection, the entire area of theinspection object die is inspected (FIG. 81) and in addition, as shownin FIG. 82, the amount of step movement in a direction perpendicular tothe scan direction is adjusted whereby thinned-out inspection can beperformed (reduction in inspection time).

After inspection, the number of defects, positions of dies includingdefects, defect sizes, defect positions in dies, defect types, defectiveimages and reference images are displayed on a display as inspectionresults, and information thereof, recipe information and the like arestored in a file, whereby results of inspection in the past can beconfirmed and reproduced.

During automatic defect inspection, various kinds of recipes areselected and designated, whereby the wafer is loaded according to thetransportation recipe, alignment of the wafer is performed on the stageaccording to the alignment recipe, focus conditions are set according tothe focus map recipe, inspection is carried out according to theinspection recipe, and the wafer is unloaded according to thetransportation recipe (FIG. 83(A) and FIG. 83(B)).

2-6-4) Control System Configuration

This apparatus is comprised of a plurality of controllers as shown inFIG. 84. A main controller conducts GUI unit/sequence operations of theapparatus (EBI), receives operation commands from a factory hostcomputer or GUI, and gives necessary instructions to a VME controllerand an IPE controller. The VME controller conducts operations ofcomponents of the apparatus (EBI), and gives instructions to a stagecontroller and a PLC controller according to the instructions from themain controller. The IPE controller acquires defect inspectioninformation from an IPE node computer, classifies the acquired defectsand displays an image according to the instructions from the maincontroller. The IPE node computer acquires an image outputted from theTDI camera and carries out defect inspection.

Upon reception of the instructions from the VME controller, the PLCcontroller drives devices such as valves, acquires sensor information,and monitors abnormalities such as a vacuum abnormality that should bemonitored all the time. Upon reception of the instructions from the VMEcontroller, the stage controller conducts movement in the XY directionand rotation of the wafer placed on the stage.

By forming such a distributed control system, interfaces between thecontrollers are kept the same to eliminate the necessity to changesoftware and hardware of the upper-level controller if an apparatuscomponent at the end is changed. Furthermore, even if a sequenceoperation is added/modified, a change in upper-level software andhardware is minimized, whereby a change in configuration can be flexiblycoped with

2-6-5) User Interface Configuration

FIG. 85 shows the device configuration of a user interface.

(1) Input Unit

The input unit is a device receiving inputs from the user, and iscomprised of a “keyboard”, a “mouse” and a “JOY pad”.

(2) Display Unit

The display unit is a device displaying information to the user, and iscomprised of two monitors.

Monitor 1: displaying an image acquired by the CCD camera or TDI camera.

Monitor 2: GUI display

Coordinate System

In this apparatus, the following three coordinate systems are specified.

(1) Stage Coordinate System [X_(S), Y_(S)]

This is a reference coordinate system for indicating a position duringcontrol of a stage position.

The X coordinate value is incremented in the rightward direction and theY coordinate value is incremented in the upward direction with the lowerleft corner of a chamber as an origin.

This apparatus has only one coordinate system as this coordinate system.

The position (coordinate values) shown in the stage coordinate system issituated at the center of the stage (center of the wafer).

That is, if the coordinate values [0,0] are designated in the stagecoordinate system, the stage is moved so that the center of the stage(center of the wafer) is superimposed on the origin of the stagecoordinate system.

[μm] is used as a unit, but the minimum resolution is λ/1024 (≈0.618[nm]).

*λ: wavelength of a laser for use in the laser interferometer (λ≈632.991[nm]).

(2) Wafer Coordinate System [X_(W), Y_(W)]

The coordinates are reference coordinates for indicating a position ofobservation (imaging/display) on the wafer.

The X coordinate value is incremented in the rightward direction and theY coordinate value is incremented in the upward direction with thecenter of the wafer as an origin.

The position (coordinate values) shown in the wafer coordinate system issituated at the center of imaging by an imaging device (CCD camera, TDIcamera) selected at this time.

This apparatus has only one coordinate system as this coordinate system.

[μm] is used as a unit, but the minimum resolution is λ/1024(≈0.618[nm]).

*λ: wavelength of a laser for use in the laser interferometer (λ≈632.991[nm]).

(3) Die Coordinate System [X_(D), Y_(D)]

The coordinates are reference coordinates for specifying a position ofobservation (imaging/display) in each die.

The X coordinate value is incremented in the rightward direction and theY coordinate value is incremented in the upward direction with the lowerleft corner of each die as an origin. This coordinate system exists ineach die. [μm] is used as a unit, but the minimum resolution is λ/1024(≈0.618 [nm]).

*λ: wavelength of a laser for use in the laser interferometer (λ≈632.991[nm]).

Furthermore, dies on the wafer are numbered (subjected to numbering),and a die serving as a reference for numbering is called an origin die.By default, the die closest to the origin of the wafer coordinate systemis the origin die, but the position of the origin die can be selectedaccording to designation by the user.

The relation between the coordinate values in each coordinate system andthe position of observation (display) is shown in FIG. 86. * Therelation between coordinates indicated by a user interface and thedirection of movement of the stage is as follows.

(1) Joystick & GUI Arrow Button

The direction indicated by a joystick and a GUI arrow button isconsidered as a direction in which the operator wants to make anobservation, and the stage is moved in a direction opposite to theindicated direction.

Example

Indicated direction: right . . . direction of movement of stage: left(image shifts to the left=field of view shifts to the right).

Indicated direction: upward . . . direction of movement of stage:downward (image shifts downward=field of view shifts upward)

(2) Direct Input of Coordinates on GUI

The coordinates directly inputted on the GUI are considered as aposition in which the operator wants to make an observation on the wafercoordinate system, and the stage is moved so that the wafer coordinatesare displayed at the center of the formed image.

2-7) Descriptions of Other Functions and Configurations

FIG. 87 shows the overall configuration of this embodiment. However,part of the configuration is omitted. In this figure, an inspectionapparatus has a primary column 87•1, a secondary column 87•2 and achamber 87•3. An electron gun 87•4 is provided in the primary column87•1, and a primary optical system 87•5 is placed on the optical axis ofan electron beam (primary beam) emitted from the electron gun 87•4.Furthermore, a stage 87•6 is placed in the chamber 87•3, and a sample Wis placed on the stage 87•6.

An objective lens 87•7, a numerical aperture 87•8, a Wien filter 87•9, asecond lens 87•10, a field aperture 87•11, a third lens 87•12, a fourthlens 87•13 and a detector 87•14 are placed on the optical axis of asecondary beam emitted from the sample W in the secondary column 87•2.Furthermore, the numerical aperture 87•12 corresponds to an aperturediaphragm, and is a thin plate made of metal (Mo) having a circularhole. The aperture is situated at the crossover position of the primarybeam and the back focal position of the objective lens 87•7. Thus, theobjective lens 87•7 and the numerical aperture 87•8 constitute atelecentric electro-optical system.

On the other hand, an output of the detector 87•14 is inputted to acontrol unit 87•15, and an output of the control unit 87•15 is inputtedto a CPU 87•16. A control signal of the CPU 87•16 is inputted to aprimary column control unit 87•17, a secondary column control unit 87•18and a stage drive mechanism 87•19. The primary column control unit 87•17controls a lens voltage of the primary optical system 87•5, thesecondary column control unit 87•18 controls lens voltages of theobjective lens 87•8 and the second to fourth lenses 87•10 to 87•13, andcontrols an electromagnetic field applied to the Wien filter 87•9.

Furthermore, the stage drive mechanism 87•19 transmits positioninformation of the stage to the CPU 87•16. Further, the primary column87•1, the secondary column 87•2 and the chamber 87•3 are connected to avacuum pumping system (not shown), and are evacuated by aturbo-molecular pump of the vacuum pumping system to maintain vacuumconditions therein.

(Primary beam) The primary beam from the electron gun 87•4 enters theWien filter 87•9 while receiving a lens action by the primary opticalsystem 87•5. Here, as a tip of the electron gun, LaB₆ enabling a largecurrent to be taken with a rectangular cathode is used. Furthermore, forthe primary optical system 72, a rotation axis-asymmetric quadrupole oroctpole electrostatic (or electromagnetic) lens is used. This can causeconvergence and divergence on the X and Y axes, respectively, as in thecase of so called a cylindrical lens. This leas is formed in two, threeor four stages, and conditions of each lens are optimized, whereby thebeam irradiation area on the sample surface can be formed into anyrectangular or elliptic shape without causing a loss of irradiationelectrons.

Specifically, if the electrostatic quadrupole lens is used, fourcircular column rods are placed around the optical axis. Oppositeelectrodes are potential-equalized, and given opposite voltagecharacteristics in phases shifted at a right angle to each other aroundthe optical axis.

Furthermore, as the quadrupole lens, a lens having a shape such that acircular plate usually used as an electrostatic deflector quadrisectedmay be used instead of a circular column lens. In this case, the lenscan be downsized. The primary beam passing through the primary opticalsystem 72 has its orbit bent by a deflection action of the Wien filter87•9. The Wien filter 87•9 orthogonalizes the magnetic field and theelectric field, makes only charged particles satisfying the Wiencondition of E=vB travel in a straight line where E is the electricfield, B is the magnetic field, and v is the velocity of chargedparticles, and bends the orbit of other charged particles. For theprimary beam, a force FB by the magnetic field and a force FE by theelectric force are produced, and thus the beam orbit is beat. On theother hand, for the secondary beam, the force FB and the force FE act inopposite directions, and are thus mutually canceled, and therefore thesecondary beam travels in a straight line.

The lens voltage of the primary optical system 87•5 is previously set sothat the primary beam is made to form an image at the aperture of thenumerical aperture 87•8. The numerical aperture 87•8 inhibits arrival atthe sample surface of an excessive electron beam scattered in theapparatus, thus preventing charge-up and contamination of the sample W.Further, since the numerical aperture 87•8 and the objective lens 87•7constitute a telecentric electro-optical system, the primary beampassing through the objective lens 87•7 is a parallel beam, and isequally and uniformly applied to the sample W. That is, Koehlerillumination is achieved as in the optical microscope.

(Secondary beam) When the primary beam is irradiated to the sample,secondary electrons, reflection electrons or back-scattered electronsare generated as secondary particles from the beam irradiation surfaceof the sample.

The secondary particles passes through the lens while receiving a lensaction by the objective lens 87•7. The objective lens 87•7 isconstituted by three electrodes. The lowermost electrode is designed toform a positive electric field with a potential on the sample W side toattract electrons (particularly secondary electrons having lowdirectivity) and guide the electrons into the lens efficiently.Furthermore, the lens action is achieved by applying a voltage to firstand second electrodes of the objective lens 87•7, and keeping the thirdelectrode at zero potential. On the other hand, the numerical aperture87•8 is situated at the position of the focus of the objective lens87•7, i.e. the position of the back focal position from the sample W.Thus, a light flux of the electron beam exiting from an acentric(off-axis) area of the field of view passes through the central positionof the numerical aperture 87•8 as a parallel beam without causing aneclipse.

Furthermore, the numerical aperture 87•8 plays a role to reduce lensaberrations of the second to fourth lenses 87•10 to 87•13 for thesecondary beam. The secondary beam passing through the numericalaperture 87•8 travels away in a straight line without receiving adeflection action of the Wien filter 87•9. Furthermore, by changing theelectromagnetic field applied to the Wien filter 87•9, only electronshaving specific energy (e.g. secondary electrons, or reflectionelectrons, or back-scattered electrons) can be guided to the detector87•14.

If secondary particles are made to form an image by the objective lens87•7 alone, the lens action becomes so strong that the aberration tendsto occur. Thus, the secondary particles are made to form an image onetime by a combination of the objective lens 87•7 and the second lens87•10. The secondary particles are subjected to intermediate imaging onthe field aperture 87•11 by the objective lens 87•7 and the second lens87•10. In this case, usually, the magnification necessary as thesecondary optical system is often insufficient, and thus as a lens formagnifying the intermediate image, the third lens 87•12 and the fourthlens 87•13 are added. The secondary particles are made to form an imageunder magnification by the third lens 87•12 and the fourth lens 87•13,respectively, i.e. they are made to form an image total three timeshere. Furthermore, they may be made to form an image one time (totaltwice) by the third lens 87•12 and the fourth lens 87•13 in combination.

Furthermore, the second to fourth lenses 87•10 to 87•13 are each arotation axis-symmetric lens called a unipotential or Einzwell lens.Each lens is comprised of three electrodes, in which two outsideelectrodes are usually at zero potential, and the lens is caused toperform a lens action and controlled with a voltage applied to thecentral electrode. Furthermore, the field aperture 87•11 is situated atthe intermediate imaging point. The field aperture 87•11 limits thefield of view to a necessary range like a field diaphragm of an opticalmicroscope, but in the case of the electron beam, an excessive beam isblocked with the third lens 87•12 and the fourth lens 87•13 to preventcharge-up and contamination of the detector 87•14. Furthermore, themagnification is set by changing the lens conditions (focal distance) ofthe third lens 87•12 and the fourth lens 87•13.

The secondary particles are projected under magnification by thesecondary optical system, and form an image on the detection surface ofthe detector 87•14. The detector 87•14 is comprised of an MCP amplifyingelectrons, a fluorescent screen converting electrons into light, a lensfor communicating between the vacuum system and the outside andtransmitting an optical image and other optical elements, and an imagingdevice (CCD, etc.). The secondary particles form an image on the MCPdetection surface and amplified, and electrons are converted intooptical signals by the fluorescent screen, and converted intophotoelectric signals by the imaging element.

The control unit 87•15 reads an image signal of the sample from thedetector 87•14, and transmits the signal to the CPU 87•16. The CPU 87•16carries out defect inspection of the pattern by template matching or thelike from the image signal. Furthermore, the stage 87•6 can be moved inthe XY direction by the stage drive mechanism 87•19. The CPU 87•16 readsthe position of the stage 87•6, outputs a drive control signal to thestage drive mechanism 87•19, drives the stage 87•6, and performsdetection and inspection of images one after another.

In this way, in the inspection apparatus of this embodiment, thenumerical aperture 87•8 and the objective lens 87•7 constitute atelecentric electro-optical system, thus making it possible to uniformlyirradiate the beam to the sample for the primary beam. That is, Koehlerillumination can easily be achieved.

Further, for secondary particles, all main beams from the sample W enterthe objective lens 87•7 at a right angle (in parallel to the lensoptical axis), and pass through the numerical aperture 87•8, andtherefore periphery light is not eclipsed, and the image brightness ofthe periphery of the sample is not reduced. Furthermore, position ofimage formation varies, i.e. a transverse chromatic aberration occursdue to variations in energy of electrons (particularly, secondaryelectrons have large variations in energy, and therefore cause a largetransverse chromatic aberration), but this transverse chromaticaberration can be inhibited by placing the numerical aperture 87•8 atthe focus point of the objective lens 87•7.

Furthermore, since the magnification is changed after the beam passesthrough the numerical aperture 87•8, a uniform image can be obtainedover the entire field of view at the detection side even if the setpowers of lens conditions of the third lens 87•10 and the fourth lens87•13 are changed. Furthermore, in this embodiment, a uniform imagehaving no unevenness can be acquired but usually, if the magnificationis increased, the problem arises such that the brightness of the imageis reduced. Thus, to solve this problem, the lens conditions of theprimary optical system are set so that when the lens conditions of thesecondary optical system are changed to change the magnification, theeffective field of view on the sample surface determined accordingly andthe electron beam irradiated to the sample surface have the same size.

That is, if the magnification is increased, the field of view is reducedaccordingly, but by increasing the current density of the electron beam,the signal density of detection electrons is kept constant, and thus thebrightness of the image is not reduced, even if the electron beam isprojected under magnification by the secondary optical system.

Furthermore, in the inspection apparatus of this embodiment, the Wienfilter 87•9 bending the orbit of the primary beam and making thesecondary beam travel in a straight line is used, but the Wien filter isnot limited to this configuration, and the apparatus may have aconfiguration using a Wien filter making the orbit of the primary beamtravel in a straight line and bending the orbit of the secondary beam.The E×B is used here, but only a magnetic field may be used. In thiscase, for example, both the direction in which primary elections enterand direction in which signal electrons are made to travel toward thedetector may follow a Y-shaped configuration

Furthermore, in this embodiment, a rectangular beam is formed from arectangular cathode and a quadrupole lens, but the invention is notlimited thereto and, for example, a rectangular or elliptic beam may bemade from a circular beam, or a circular beam may be made to passthrough a slit to take a rectangular beam. Furthermore, either a linearbeam or a plurality of beams may be used, and they may be scanned.

2-7-1) Control Electrode

An electrode approximately axisymmetric to an irradiation optical axisof an electron beam (25•8 in FIG. 25-1) is placed between the objectivelens 87•7 and the wafer W. Examples of the shape of the electrode areshown in FIGS. 88 and 89. FIGS. 88 and 89 are perspective views ofelectrodes 88•1 and 89•1. FIG. 88 is a perspective view showing theelectrode 88•1 having an axisymmetrically cylindrical shape, and FIG. 89is a perspective view showing the electrode 89•1 having anaxisymmetrically discoid shape.

In this embodiment, the electrode 88•1 having a cylindrical shape shownin FIG. 88 is used, but the electrode 89•1 having a discord shape shownin FIG. 89 may be used as long as it is approximately axisymmetric tothe irradiation optical axis of the electron beam. Further, apredetermined voltage (negative potential) lower than a voltage appliedto the wafer W (potential is 0 V because the wafer W is grounded in thisembodiment) is applied to the electrode 88•1 by the power supply 25•9 togenerate an electric field for preventing a discharge between theobjective lens 87•7 (25•7 in FIG. 25-1) and the wafer W. A potentialdistribution between the wafer W and the objective lens 97•7 at thistime will be described with reference to FIG. 90.

FIG. 90 is a graph showing a voltage distribution between the wafer Wand the objective lens 87•7. This figure shows a voltage distributionfrom the wafer W to the position of the objective lens 87•7 with theposition on the irradiation optical axis of the electron beam as ahorizontal axis. In the conventional electron beam apparatus having noelectrode 88•1, the voltage distribution from the objective lens 87•7 tothe wafer W gently changes up to the grounded wafer W with the voltageapplied the objective lens 87•7 being the maximum (narrow line in FIG.90), while in the electron beam apparatus of this embodiment, theelectrode 88•1 is placed between the objective lens 87•7 and the waferW, and a predetermined voltage (negative potential) lower than a voltageapplied to the wafer is applied to the electrode 88•1, so that theelectric field of the wafer W is weakened (thick line in FIG. 90).Accordingly, in the electron beam apparatus of this embodiment, theelectric field is not concentrated near the via 25•13 in the wafer (FIG.25-1), and thus the electric field is not increased. If the electronbeam is applied to the via 25•13 to emit secondary electrons, theemitted secondary electrons are not accelerated to the extent thatresidual gas is ionized, thus making it possible to prevent a dischargeoccurring between the objective lens 87•7 and the wafer W.

Furthermore, since a discharge can be prevented between the objectivelens 87•7 and the via 25•13 (FIG. 25-1), there is no possibility thatthe pattern of the wafer W and the like are damaged with discharge.Furthermore, in the embodiment described above, a discharge between theobjective lens 87•7 and the wafer W having the via 25•3 can beprevented, but since a negative potential is applied to the electrode88•1, the efficiency of detection of secondary electrons by the detector87•14 may be reduced. Accordingly, if the detection efficiency isreduced, a series of operations of irradiating the electron beam todetect secondary electrons are carried out two or more times, and aplurality of obtained detection results are subjected to processing suchas cumulative addition and equalization to obtain a predetermined signalquality (S/N ratio of signal). This embodiment is described using asignal to noise ratio (S/N ratio) as the detection efficiency as oneexample.

The secondary electron detection operation will now be described withreference to FIG. 91. FIG. 91 is a flowchart showing the secondaryelectron detection operation of the electron beam apparatus. First,secondary electrons from an inspection subject sample are detected bythe detector 87•14 (step 91•1). Then, whether the signal to noise ratio(S/N ratio) is equal to or greater than a predetermined value or not isdetermined (step 91•2). If the signal to noise ratio is equal to orgreater than the predetermined value at step 91•2, it means thatsecondary electrons have been detected sufficiently by the detector87•14, and thus the secondary electron detection operation is ended.

On the other hand, if the signal to noise ratio is smaller than thepredetermined value at step 91•2, a series of operations of irradiatingthe electron beam to detect secondary electrons are carried out 4Ntimes, and equalization processing is carried out (step 91•3). Here,since the initial value of N is set to “1”, the secondary electrondetection operation is carried out 4 times at the initial round at step91•3.

Then, “1” is added to N to count up (step 91•4), and again whether thesignal to noise ratio is equal to or greater than the predeterminedvalue is determined at step 91•2. Here, if the signal to noise ratio issmaller than the predetermined value, processing proceeds to step 91•3again, where the secondary electron detection operation is carried out 8times in this case. Then, N is counted up, and steps 91•2 to 91•4 arerepeated until the signal to noise ratio is equal to or greater than thepredetermined value.

Furthermore, in this embodiment, a predetermined voltage (negativepotential) lower than a voltage applied to the wafer W is applied to theelectrode 88•1 to prevent a discharge to the wafer W having the via25•13 but in this case, the efficiency of detection of secondaryelectrodes may be reduced. Accordingly, if the inspection subject sampleis a type of inspection subject sample hard to cause a discharge betweenitself and the objective lens 87•7, such as a wafer having no via, thevoltage applied to the electrode 88•1 can be controlled so that theefficiency of detection of secondary electrons in the detector 87•14 isimproved.

Specifically, even when the inspection subject sample is grounded, apredetermined voltage higher than the voltage applied to the inspectionsubject sample, for example a voltage of +10 V is applied to theelectrode 88•1. Furthermore, at this time, the distance between theelectrode 88•1 and the inspection subject sample is set to a distancesuch that no discharge occurs between the electrode 88•1 and theinspection subject sample.

In this case, secondary electrons generated by irradiation of theelectron beam to the inspection subject sample are accelerated towardthe detector 87•14 side by an electric field generated with the voltageapplied to the electrode 88•1. The secondary electrons are furtheraccelerated toward the detector 87•14 side with an electric fieldgenerated with a voltage applied to the objective lens 87•7 andsubjected to a convergence action, and therefore a large number ofsecondary electrons enter the detector 87•14, thus making it possible tothe detection efficiency.

Furthermore, the electrode 88•1 is axisymmetric, and thus has a lensaction for convergence of the electron beam applied to the inspectionsubject sample. Thus, the primary electron beam can be more finelyfocused with the voltage applied to the electrode 88•1. Furthermore,since the primary electron beam can be finely focused with the electrode88•1, an objective lens system having a lower aberration can be formedwith a combination with the objective lens 87•7. The electrode 88•1 maybe approximately axisymmetric to the extent that this lens action can beachieved.

According to the electron beam apparatus of the embodiment describedabove, an electrode having a shape approximately axisymmetric to theirradiation axis of the electron beam and controlling the intensity ofthe electric field on the surface of the inspection subject sampleirradiated with the electron beam is provided between the inspectionsubject sample and the objective lens, thus making it possible tocontrol the electric field between the inspection subject sample and theobjective lens.

An electrode having a shape approximately axisymmetric to theirradiation axis of the electron beam and reducing the intensity of theelectric field on the surface of the inspection subject sampleirradiated with the electron beam, thus making it possible to eliminatea discharge between the inspection subject sample and the objectivelens. Furthermore, since alterations such as reduction of the voltageapplied to the objective lens are not made, secondary electrons can bemade to pass through the objective lens efficiently, thus making itpossible to improve the detection efficiency and obtain a signal havinga good S/N ratio.

The voltage for reducing the intensity of the electric field on thesurface of the inspection subject sample irradiated with the electronbeam can be controlled depending on the type of inspection subjectsample. For example, if the inspection subject sample is a type ofinspection subject sample that tends to cause a discharge between itselfand the objective lens, the discharge can be prevented by changing thevoltage of the electrode to reduce the intensity of the electric fieldon the surface of the inspection subject sample irradiated with theelectron beam.

The voltage given to the electrode can be changed, i.e. the voltage forreducing the intensity of the electric field on the surface of asemiconductor wafer irradiated with the electron beam can be changed.For example, if the inspection subject sample is a type of inspectionsubject sample that tends to cause a discharge between itself and theobjective lens, a discharge especially in the via or around the via canbe prevented by changing the electric field by the electrode to reducethe intensity of the electric field on the surface of the inspectionsubject sample irradiated with the electron beam. Furthermore, since adischarge between the via and the objective lens can be discharged, thepattern of the semiconductor wafer or the like is never damaged withdischarge. Furthermore, since the potential given to the electrode islower than the charge given to the inspection subject sample, theintensity of the electric field on the surface of the inspection subjectsample irradiated with the electron beam can be reduced, thus making itpossible to prevent a discharge to the inspection subject sample. Sincethe potential given to the electrode is a negative potential, and theinspection subject sample is grounded, the intensity of the electricfield on the surface of the inspection subject sample irradiated withthe electron beam can be reduced, thus making it possible to prevent adischarge to the inspection subject sample.

Use of the control electrode for the purpose of preventing a dischargehas been mainly described, but the control electrode may be used forscreening energy of secondary electrons emitted from the wafer. That is,if only secondary electrons having energy at a certain level or greater,which have highest signal detection efficiency, are detected, and so on,to obtain an image of high resolution, a predetermined negative voltagecan be applied to the control electrode, and the control electrode canbe used as a barrier of energy of secondary electrons. Since a negativepotential is applied to the control electrode, a force repellingsecondary electrons back to the sample is exerted. Secondary electronsincapable of passing over this potential barrier go back to the sample,and only secondary electrons passing over the potential barrier aredetected by the detector, thus making it possible to obtain an imagehaving a desired resolution.

2-7-2) Potential Application Method

In FIG. 92, a potential application mechanism 92•1 controls generationof secondary electrons by applying a potential of ±several volts to amounting table of a stage on which the wafer is placed, based on thefact that information of secondary electrons emitted from the waferdepends on the potential of the wafer. Furthermore, this potentialapplication mechanism also plays a role to attenuate energy originallypossessed by irradiation electrons so that irradiation electron energyof about 100 to 500 eV is applied to the wafer.

As shown in FIG. 92, the potential application mechanism 92•1 comprisesa voltage application apparatus 92•4 electrically connected to a holdingsurface 92•3 of a stage apparatus 92•2, and a charge-up examination anda voltage determination system (hereinafter referred to as anexamination and determination system) 92•5. The inspection anddetermination system 92•5 comprises a monitor 92•7 electricallyconnected to an image formation unit 92•6 of the detection system of theelectro-optical apparatus 13•8 (FIG. 13), an operator 92•8 connected tothe monitor 92•7, and a CPU 92•9 connected to the operator 92•84. TheCPU 92•9 supplies signals to the voltage application apparatus 92•4.

The potential application mechanism described above is designed tosearch for a potential at which the wafer as an inspection object ishard to be charged, and apply the potential.

A method for inspecting electric defects of the inspection sample mayuse the fact the interest area has a different voltage in the case wherethe interest area is electrically conductive with an originallyelectrically insulated area.

Specifically, first, a charge is previously given to the sample to causea difference between the voltage of the originally electricallyinsulated area and the voltage of the area that is originallyelectrically insulated but becomes electrically conductive by somecause, then the beam of the present invention is applied to acquire dataof the difference in voltage, and the acquired data is analyzed todetect that the area is electrically conductive.

2-7-3) Electron Beam Calibration Method

In FIG. 93, an electron beam calibration mechanism 93•1 comprises aplurality of faraday cups 93•4 and 93•5 for measurement of beamcurrents, placed at a plurality of locations on the side part of aholding surface 93•3 of the wafer on a rotation table 93•2. The faradaycup 93•4 is for a narrow beam (about φ2 μm), and the faraday cup 93•5 isfor a thick beam (about φ2 μm). For the faraday cup 93•4 for a narrowbeam, the rotation table 93•2 is moved stepwise to measure a beamprofile, while for the faraday cup 93•5 for a thick beam, the totalamount of current of the beam is measured. The faraday cups 93•4 and93•5 are arranged so that the upper surfaces are at the same level ofthe upper surface of the wafer W placed on the holding surface 93•3. Inthis way, the primary electron beam emitted from the electron gun isalways monitored. This is because the electron gun cannot always emit aconstant electron beam, but the emission is changed with time.

2-7-4) Cleaning of Electrode

When the electron beam apparatus of the present invention is activated,a target material is floated by a proximity interaction (charge ofparticles near the surface) and attracted to a high-pressure area, andtherefore organic materials are deposited on various electrodes for usein formation and deflection of the electron beam. Insulating materialsthat are gradually deposited with the charge of the surface badly affectformation of the electron beam and the deflection mechanism, andtherefore the deposited insulating materials must be removedperiodically. The periodic removal of insulating materials is carriedout by producing plasmas of hydrogen, oxygen or fluorine and compoundscontaining those elements such as HF, O₂, H₂O and C_(M)F_(N) undervacuum using electrodes near the area on which insulating materials aredeposited, and keeping the plasma potential in a space at a potential(several kVs, e.g. 20 V to 5 kV) at which spatters occur on the surfaceof the electrode to oxidize, hydrogenise and fluorinate only organicmaterials. Furthermore, by passing a gas having a cleaning effect,contaminants on the surfaces of the electrode and the insulator can beremoved

2-7-5) Alignment Control Method

An alignment control apparatus 94•1 of FIG. 94 is an apparatuspositioning the wafer W with respect to an electro-optical apparatus94•2 using a stage apparatus, and performs control such as roughadjustment of the wafer by a wide-field observation using an opticalmicroscope 94•3 (measurement under a lower magnification thanmeasurement by the electro-optical system), adjustment under a highmagnification using an electro-optical system of the electro-opticalapparatus 94•2, focus adjustment, setting of an inspection area, patternalignment. The reason why the wafer is inspected under a lowmagnification using an optical system is that an alignment mark shouldbe easily detected with an electron beam when the pattern of the waferis observed to perform wafer alignment in a narrow-field using theelectron beam to automatically inspect the pattern of the wafer.

The optical microscope 94•3 is provided in a housing (may be movablyprovided in the housing), and a light source (not shown) for operatingthe optical microscope is housed. Furthermore, the electro-opticalsystem (primary optical system and secondary optical system) of theelectro-optical apparatus 94•2 is also used as an electro-optical systemfor making an observation under a high magnification. The outlinedconfiguration thereof is shown in FIG. 94. To observe an observationsubject point on the wafer under a low magnification, an X stage on thestage apparatus is moved in the X direction to shift the observationsubject point on the wafer to within the field of view of the opticalmicroscope. The wafer is visually recognized in a wide field with theoptical microscope 94•3, the position of the wafer to be observed isdisplayed on a monitor 94•5 via a CCD 94•4, and the observation positionis roughly determined. In this case, the magnification of the opticalmicroscope may be changed from a low magnification to a highmagnification.

Then, the stage apparatus is moved by a distance equivalent to aninterval δx between the optical axis of the electro-optical apparatus94•2 and the optical axis of the optical microscope 94•3 to shift theobservation subject point on the wafer predefined by the opticalmicroscope to the position of the field of view of the electro-opticalapparatus. In this case, a distance δx between the axial line O₃-O₃ ofthe electro-optical apparatus and the optical axis O₄-O₄ of the opticalmicroscope 94•3 (both axes are deviated in position only along thedirection of the X axis in this embodiment, but may be deviated inposition along the direction of the Y axis and the direction of the Yaxis) is already know, and therefore movement of the stage apparatus bythe value δx can shift the observation subject point to the visuallyrecognized position. After the shift of the observation subject point tothe visually recognized position of the electro-optical apparatus iscompleted, the observation subject point is SEM-imaged under a highmagnification by the electro-optical system, and the image is stored ordisplayed on a monitor 94•7 via a CCD 94•6.

After the observation point on the wafer is displayed on the monitorunder a high magnification with the electro-optical system in this way,a positional deviation in the direction of rotation of the wafer withrespect to the center of rotation of the rotation table of the stageapparatus, and a deviation δθ in the direction of rotation of the waferwith respect to the optical axis O₃-O₃ of the electro-optical system aredetected, and a deviation in position in the X and Y axes of apredetermined pattern with respect to the electro-optical system isdetected. The operation of the stage apparatus 94•8 is controlled basedon the detected value and separately obtained data of an inspection markprovided on the wafer or data about the shape of the pattern of thewafer to perform alignment of the wafer. The range of alignment iswithin ±10 pixels in XY coordinates. It is preferably within ±5 pixels,more preferably within ±2 pixels.

2-7-6) EO Correction

A. Overview

When the beam from the wafer is imaged with a TDI, the wafer should becorrectly positioned but actually, the wafer is placed on the X-Y stageand mechanically positioned, and hence the accuracy is in the range ofseveral hundreds of nm to several tens of μm, and the response time isseveral seconds to several milliseconds as practical values.

On the other hand, the design rule is refined toward several tens of nm,and thus wiring with the line width of several tens of nm and vias withthe diameter of several tens of nm should be inspected to detect theirshape defects and electric defects, and dust with the diameter ofseveral tens of nm. Imaging dependent solely on the mechanicalpositioning results in a significant difficulty in acquirement of acorrect image because the order of the response time and positioningaccuracy considerably differs from the order of the design rule andimaging accuracy.

A sequence of imaging is carried out by a combination of a step (x axis)and a constant speed scan (y axis), and relatively dynamic control (yaxis) generally has a large control residual, and thus is required to behigh level control for preventing a blur of an image.

In view of these items, an X-Y stage having high accuracy and excellentresponsivity is provided as a matter of course, but further a functionof EO correction is provided to achieve accuracy of control of the beamfor an imaging unit and a speed, which cannot be ensured by the stage.

The fundamental method is such that the position of the wafer on thestage is correctly recognized within a time delay of several microseconds in the order of sub nm with a laser interferometer and a barmirror placed on the x-y axis, a mechanical actuator is driven by anautomatic control loop, and the wafer is positioned at a target positionwith a temporal delay and a residual. The control residual as a resultof positioning by this control is determined by a difference between thetarget position generated within a control apparatus and the currentposition obtained by a laser interferometer system. On the other hand,the beam passes through various electrodes, and is then guided to animaging apparatus via a deflection electrode for correction. Thedeflection electrode for correction has a sensitivity capable ofdeflection within about several hundreds of μm, preferably within ahundred μm, more preferably within several tens of μm equivalent to thedistance on the wafer, and by applying a voltage to the electrode, thebeam can be deflected to any position on a two-dimensional basis. Thecontrol residual is subjected to calculation by a calculation apparatus,and then converted into a voltage by a D/A converter, and the voltage isapplied to the deflection electrode for correction in a direction foroffsetting the residual. The above configuration makes it possible tocarry out correction close to the resolution of the laserinterferometer.

As another method, the mean described above is used for the X axis (stepdirection), and a transfer clock of the TDI as an imaging device istransferred in synchronization with the speed of movement of the stagefor the Y axis.

The concept of EO correction is shown in FIG. 95. An indication 95•1 toa target position is outputted, and given to a control feedback loop95•2 including a mechanical actuator. This part corresponds to a stage.The result of occurrence of a positional displacement by driving issubjected to feedback by a position detector 95•3, and the positionaldisplacement of a drive system converses into the target position fromthe position indication, but a gain of a control system is finite, andtherefore a residual occurs. The current position is detected in theorder of sub nm by a position output system 95•4 (a laser interferometeris used here), a difference with the position indication apparatus 95•1is detected by a residual detector 95•5, a voltage is applied to adeflection electrode 95•7 using a high-pressure and high-speed amplifier95•6, a voltage is applied in a direction for offsetting the residual,and if this function is not originally provided, a function to reduce agenerated variation as denoted by reference numeral 95•8 to a variationdenoted by a reference numeral 95•9 is provided.

The specific configuration of devices is shown in FIG. 96. An XY stage96•1 drives the X axis with a servo motor 96•2 for driving the X axisand an encoder 96•3, and detects a rough position thereof and a speed toachieve smooth servo characteristics. In this example, the servo motoris used, but a similar configuration can be provided with an actuatorsuch as a linear motor or ultrasonic motor. Reference numeral 96•6denotes a power amplifier for driving the motor. Precise positioninformation of the X axis achieves a position detection function havinga resolution in sub nm by a combination of a mirror 96•7, aninterferometer 96•8, a receiver 96•9, a laser light source 96•10 and aninterferometer board 96•11.

The Y axis functions similarly to the X axis orthogonal thereto, and iscomprised of a servo motor 96•12, an amplifier 96•13, a mirror 96•14, aninterferometer 9•5 and a receiver 96•16.

An X-Y stage controller 96•17 collectively controls these devices,thereby enabling the stage to be moved two-dimensionally, achievesaccuracy of 1000 μm to 1 nm, preferably 100 μm to 2 nm, more preferably1 μm to 2 nm, further more preferably 0.1 μm to 2 nm, and achieves aperformance such that the response tune is several thousands ofmilliseconds or less, preferably several tens of milliseconds, morepreferably several milliseconds. On the other hand, an X reference valueand a Y reference value are outputted from the X-Y stage controller96•17 to an EO corrector 96•18, position information is outputted in a32 bit binary format from the interferometer 96•11, and the EO corrector96•18 receives the current position via a high-speed buffer board 96•19.Calculation is internally performed, then a voltage is amplified withhigh-voltage and high-speed amplifiers 96•20 and 96•21, then the voltageis applied to a deflection electrode 96•22, and deflected for correctionof a residual, and an image information electron beam with a positionaldeviation reduced to a minimum is guided to a TDI (imaging device)96•23. Reference numeral 96•24 denotes a portion for generating a timingsignal for determining a transfer speed of the TDI 96•23 as describedlater.

A function of generating a target position in the scan direction in thisapparatus will now be described. EO correction is a function ofdetermining a difference between the target position and the actualposition, deflecting the electron beam so as to offset the difference tocorrect the position, but the correction range is limited to a range ofabout several tens of μm. This is determined by an electrodesensitivity, a dynamic range of the high-voltage and high-speedamplifier, a noise level, and the number of bits of the D/A converter.However, the actual position of the stage during scanning isconsiderably deviated with respect to the target position, compared withthe position when the stage is stopped, due to the fact that the gain ofthe control loop is finite. If the stage travels at 20 mm/s, thedifference between the actual position and the target position is about400 μm, and the correction range is considerably exceeded to saturatethe system if the difference is calculated and outputted directly.

To prevent such a phenomenon, this apparatus uses the following means toavoid problems. The concept thereof is shown in FIG. 97.

A position 97•1 is the target position of the stage, and is lineallyincremented with time because the stage is moved at a constant speedduring scanning. On the other hand, a mechanical position 97•2 of thestage as a result of actually being controlled includes mechanicalvibrations of several microns and has a steady-state deviation 97•3 ofabout 400 μm. As a measure for removing this steady-state deviation, itcan be considered that a filter is used to smooth position informationwhen the stage travels but in this case, there is a disadvantage that adelay absolutely occurs due to a time constant of the filter, and if atime constant such that a ripple is negligible is provided, ameasurement starting area is strictly limited, leading to a considerableincrease in overall measurement time. Thus, in this proposal, fordetecting this steady-state deviation, at least a difference between thecurrent position at the time of previous scanning and the targetposition is integrated at least about 2¹⁶ times, the resulting value isdivided by the number of samples to determine an average value 97•4 ofthe steady-state deviation between the target position and the currentposition, and calculation is performed as a target position 97•6synthesized by subtracting an average value 97•4 from a target position97•5 during present scanning to achieve a configuration enabling EOcorrection to be performed within the dynamic range as shown by 98•1 ofFIG. 98. Furthermore, the number of integrations are not limited to thisvalue, but may be a smaller number of integration stages as long as atarget level of accuracy is obtained.

FIG. 99 is a block diagram. A current position 99•2 is subtracted from atarget value 99•1, and the integration calculation is carried out withina block of 99•3 during scanning. On the other hand, the average value ofthe steady-state deviation previously determined in the same manner isoutputted to a position 99•3 from a position 99•4. The position 99•4 issubtracted from the target value 99•1 to obtain a synthesized targetposition 99•6 by a subtractor 99•5, and this value is subtracted from acurrent position 99•7 from an interferometer to achieve EO correctiondata free from a delay in response and a ripple.

FIG. 100 shows a structure of detection of an average of a difference ofa block of 99•3 in FIG. 99. Integration is carried out by an ALU 100•1and a latch 100•2, a word of a data selector 100•4 is selected by avalue of a cumulative time counter 100•3, calculation equivalent todivision is carried out, and an average value of the steady-statedeviation is outputted.

An idea of a transfer clock of the TDI is shown in FIG. 101. The TDI isan imaging device having photo-electric elements connected in a multiplestage in the scan direction, and transmitting charges of imaging devicesto subsequent devices to improve the sensitivity and reduce randomnoises, but as shown in FIG. 101, it is important that imaging objectson the stage correspond to pixels on the TDI on a one-to-one basis, andif this relation is broken, an image is blurred. Synchronous relationsare shown in FIGS. 1-1, 1-2, 2-1 and 2-2, and asynchronous relations areshown in FIGS. 3-1, 3-2, 4-1 and 4-2. Since the TDI is transferred to anext stage in synchronization with an external pulse, this is achievedby generating a transfer pulse when the stage is moved in an amountequivalent to one pixel.

However, the output of position information in a laser interferometerthat is in the mainstream takes a form of outputting a 32 bit binaryoutput in synchronization with its own internal clock of 10 MHz, andthus this cannot be easily achieved in the original state. Furthermore,if the resolution is several tens of nm, the accuracy of the transferpulse is also important, and thus high-speed and high-accuracy digitalprocessing is required. A method devised in the invention is shown inFIG. 102. In this figure, position information of the interferometer anda synchronization signal of 10 MHz are introduced into a main circuitvia a buffer 102•1. A 10 MHz clock 102•2 generates a clock of 100 MHzsynchronized with a PLL 102•3, and supplies the same to each circuit.Calculation processing is carried out for every 10 states of thissynchronization signal 102•4. Present position information is retainedin a latch 102•5, and a pervious value is retained in a latch 102•6. Adifference between both the values is calculated by an ALU 102•7, and adifference of positions for every 10 states is outputted from acomponent 102•8. This difference value is loaded to a parallel serialcomparator 102•9 as a parallel value, and outputted from an OR 102•10 asa number of serial pulses in synchronization with the clock of 100 MHz.A comparator 102•11 has a similar function, but is configured to becapable of operating continuously for every 10 states in combinationwith components 102•12 and 102•13. As a result, a serial pulse matchinga position difference is outputted from a summation circuit 102•10 to acounter 102•14 for every 10 MHz. Provided that the resolution of thelaser interferometer is 0.6 nm and one pixel has a size of 48 nm, 19pulses are outputted at the time when the counter becomes equivalent toone pixel if a comparator 102•15 is set at 80. Use of this signal as atransfer pulse from outside the TDI allows an operation synchronizedwith even a variation in stage speed, thus making it possible to preventblurring.

A timing chart is shown in FIG. 103. Reference numeral 1 denotesinterferometer coordinate (position) information, in which numbers showpositions as examples. Reference numeral 2 denotes a synchronizationsignal of 100 MHZ created by a PLL. A bank A is operation timing of theparallel serial converter 102•9, and a bank B is operation timing of thecomparator 102•11. After latch timing 7 for storing positioninformation, difference calculation timing 8 is executed, a value isloaded to the parallel serial converter 102•9, time of one cycle of anext 10 M clock 3 is used to execute an output of 4. The bank B carriesout a similar operation in timing delayed by one cycle of the 10 M clock3 to achieve pulse generation of 6 without difficulties.

2-7-7) Image Comparison Method

FIG. 104 shows the outlined configuration of a defect inspectionapparatus according to an alteration example of the present invention.The defect inspection apparatus is the projection type inspectionapparatus described above, and comprises an electron gun 104•1 emittinga primary electron beam, an electrostatic lens 104•2 deflecting andshaping the emitted primary electron beam, an E×B deflector 104•3deflecting the shaped primary electron beam so that the primary electronbeam impinges upon the semiconductor wafer W at almost a right angle ina field where an electric field E and a magnetic filed B are orthogonal,an objective lens 104•4 making the deflected primary electron beam forman image on the wafer W, a stage 104•5 provided in a sample chamber (notshown) capable of being evacuated and movable in a horizontal plane withthe wafer W placed thereon, an electrostatic lens 104•6 of a projectionsystem magnifying and projecting a secondary electron beam and/or areflection electron beam emitted from the wafer W with irradiation ofthe primary electron beam under a predetermined magnification to form animage, a detector 104•7 detecting the formed image as a secondaryelectron image of the wafer, and a control unit 104•8 controlling theentire apparatus, and carrying out processing for detecting defects ofthe wafer based on the secondary electron image detected by the detector104•7. Furthermore, not only secondary electrons but also scatteredelectrons and reflection electrons contribute to the secondary electronimage described above, but it is called a secondary electron imageherein.

Furthermore, a deflection electrode 104•9 deflecting with the electricfield or the like an angle at which the primary electron beam enters thewafer is provided between the objective lens 104•4 and the wafer W. Adeflection controller 104•10 controlling the electric field of thedeflection electrode is connected to the deflection electrode 104•9. Thedeflection controller 104•10 is connected to the control unit 104•8, andcontrols the deflection electrode so that an electric field matching acommand from the control unit 104•8 is generated in the deflectionelectrode 104•9. Furthermore, the deflection controller 104•10 can beformed as a voltage control apparatus controlling a voltage given to thedeflection electrode 104•9.

The detector 104•7 may have any configuration as long as the secondaryelectron image formed by the electrostatic lens 104•6 can be convertedinto a signal capable of being subjected to post-processing. Forexample, as shown in detail in FIG. 62, the detector 104•7 may comprisea micro-channel plate 62•1, a fluorescent screen 62•2, a relay opticalsystem 62•3, and an imaging sensor 62•4 constituted by a large number ofCCD elements. The micro-channel plate 62•1 has a large number ofchannels in a plate, and further generates a large number of electronswhile secondary electrons made to form an image by the electrostaticlens 104•6 pass through the channels. That is, secondary electrons areamplified. The fluorescent screen 62•2 converts secondary electrons intolight by emitting fluorescence with amplified secondary electrons. Therelay lens 62•3 guides the fluorescence to the CCD imaging sensor 62•4,and the CCD imaging sensor 62•4 converts an intensity distribution ofsecondary electrons on the surface of the wafer W into an electricsignal for each element, i.e. digital image data, and outputs the sameto the control unit 104•8. Here, the micro-channel plate 62•1 may beomitted and in this case, blurring caused by expansion between themicro-channel plate 62•1 and the fluorescent screen can be reduced. Forexample, an image of 0.2 in MTF can be enhanced to 0.3-0.6.

The control unit 104•8 may be constituted by a general personal computeror the like as illustrated in FIG. 104. This computer comprises acontrol unit main body 104•11 for various kinds of control andcalculation processing according to a predetermined program, a CRT104•12 displaying the result of processing by the main body 104•11, andan input unit 104•13 such as a keyboard and a mouse for an operator toinput instructions. Of course, the control unit 104•8 may be constitutedby hardware dedicated to defect inspection apparatus, a workstation orthe like.

The control main body 104•11 is comprised of a CPU, a RAM, a ROM, a harddisk, various kinds of control boards such as a video board, and thelike (not shown). A secondary electron image storage area 104•14 forstoring electric signals received from the detector 104•7, i.e. digitalimage data of the secondary electron image of the wafer W is assignedonto a memory of a RAM or hard disk. Furthermore, a reference imagestorage unit 104•15 for storing in advance reference image data of thewafer having no defects exists on the hard disk. Furthermore, inaddition to a control program for controlling the entire defectinspection apparatus, a defect detection program 104•16 for readingsecondary electron image data from the storage area 104•14 andautomatically detecting defects of the wafer W according to apredetermined algorithm based on the image data is stored on the harddisk. As describe in detail later, this defect detection program 104•16has a function that the reference image read from the reference imagestorage unit 104•15 and an actually detected secondary electron imageare made to match each other to automatically detect defective areas,and if it is determined that defects exist, warning display is providedto the operator. At this time, a secondary electron image 104•17 may bedisplayed on a display unit of the CRT 104•12.

The action of the defect inspection apparatus according to theembodiment will now be described using flowcharts of FIGS. 105 to 107 asan example. First, as shown in the flow of a main routine of FIG. 105,the wafer W as an inspection object is set on the stage 104•5 (step105•1). A large number of wafers stored in a loader may be all set onthe stage 104•5 on one-by-one basis as described previously.

Then, images of a plurality of inspection subject areas mutuallydisplaced and partially overlapping on the XY plane of the surface ofthe wafer W are each acquired (step 105•2). The plurality of inspectionsubject areas, images of which are to be acquired, are, for example,rectangular areas denoted by reference numerals 108•2 a, 108•2 b, . . ., 108•2 k, . . . on a wafer inspection surface 108•1, and it can beunderstood that these areas are mutually displaced while partiallyoverlapping around an inspection pattern 108•3 of the wafer. Forexample, as shown in FIG. 109, images 109•1 (inspection subject images)of 16 inspection subject areas are acquired. Here, in the image shown inFIG. 109, a rectangular cell corresponds to one pixel (or may be a blockunit larger than a pixel), and black-painted cells correspond to animage area of the pattern on the wafer W. The details of the step 105•2will be described later with the flowchart of FIG. 106.

Then, image data of the plurality of inspection subject areas acquiredat step 105•2 are each compared with reference image data stored in thestorage unit 104•15 (step 105•3 in FIG. 105) to determine whether or notdefects exist on the wafer inspection surface covered by the pluralityof inspection object areas. In this step, processing of so calledmatching between image data is carried out, and the details thereof willbe described later with the flowchart of FIG. 107.

If it is determined that defects exist on the wafer inspection surfacecovered by the plurality of inspection subject areas (positivedetermination in step 105•4) as a result of comparison at step 105•3,the operator is warned of existence of defects (step 105•5). As a methodfor warning, for example, a message indicating existence of defects isdisplayed on the display unit of the CRT 104•12, and an enlarged image104•17 of a pattern having defects may be displayed at the same time.The defective wafer may be immediately taken out from the samplechamber, and stored at a storage site different from that for the waferhaving no defects (step 105•6).

If it is determined that the wafer W has no defects (negativedetermination in step 105•4) as a result of comparison at step 105•5,whether any area to be inspected still exists or not is determined forthe wafer W that is currently an inspection object (step 105•7). If anarea to be inspected still exists (positive determination in step105•7), the stage 104•5 is driven to move the wafer W so that other areato be inspected next is included in the area of irradiation with theprimary electron beam (step 105•8). Then, processing returns to step105•2, where the same processing is repeated for the other inspectionarea.

If no area to be inspected exists (negative determination in step105•7), or after the step of taking out the defective wafer (step105•6), whether the wafer W that is currently an inspection object is alast wafer or not, i.e. whether or not any wafer that has not beeninspected yet still exists on a loader (not shown) is determined (step105•9). If the wafer W is not a last wafer (negative determination instep 105•9), the inspected wafer is stored at a predetermined storagesite and instead, a new wafer that has not been inspected is set on thestage 104•5 (step 105•10). Then, processing returns to step 105•2, wherethe same processing is repeated for the wafer. If the wafer W is thelast wafer (positive determination in step 105•9), the inspected waferis stored at the predetermined storage site to complete all the steps.An identification number is assigned to each cassette or each wafer, andthe wafer being inspected is recognized and monitored to preventduplicated inspection of a wafer, for example.

The flow of processing at step 105•2 will now be described according tothe flowchart of FIG. 106. In this figure, first, an image number I isset to an initial value 1 (step 106•1). The image number is anidentification number assigned sequentially to each of a plurality ofinspection subject area images. Then, an image position (X_(i), Y_(i))is determined for the inspection subject area of the set image number i(step 106•2). This image position is defined as a specified position inthe area for demarcating the inspection subject area, for example acentral position of the area. At present, the image position is (X₁, Y₁)because i equals 1, this corresponds to, for example, the centralposition of an inspection subject area 108•2 a shown in FIG. 108. Theimage positions of all inspection subject image areas are defined inadvance, and are stored on the hard disk of the control unit 104•8, forexample, and read at step 106•2.

Then, the deflection controller 104•10 applies a potential to thedeflection electrode 104•9 so that the primary electron beam passingthrough the deflection electrode 104•9 of FIG. 104 is applied to theinspection subject image area of the image position (X_(i), Y_(i))determined at step 106•2 (step 106•3 of FIG. 106).

Then, the primary electron beam is emitted from the electron gun 104•1,and applied to the surface of the set wafer W through the electrostaticlens 104•2, the E×B deflector 104•3, the objective lens 104•4 and thedeflection electrode 104•9 (step 106•4). At this time, the primaryelectron beam is deflected by an electric field produced by thedeflection electrode 104•9, and applied over the entire inspectionsubject image area at the image position (X_(i), Y_(i)) on the waferinspection surface 108•1. If the image number i equals 1, the inspectionsubject area is an area 108•2 a.

Secondary electrons and/or reflection electrons (hereinafter referred toas only “secondary electrons”) are emitted from the inspection subjectarea of irradiation with the primary electron beam. Then, the generatedsecondary electron beam is made to form an image on the detector 104•7under a predetermined magnification by the electrostatic lens 104•6 ofan enlargement projection system. The detector 104•7 detects thesecondary electron beam made to form an image, and converts the imageinto an electric signal or digital image data for each detecting elementand outputs the same (step 106•5). Detected digital image data with theimage number of i is transferred to the secondary electron image storagearea 104•14 (step 106•6).

Then, the image number i is incremented by 1 (step 106•7), and whetherthe incremented image number (i+1) exceeds a fixed value i_(MAX) or notis determined (step 106•8). This value i_(MAX) is the number ofinspection subject images to be acquired, and equals “16” in the exampleof FIG. 109 described above.

If the image number i does not exceed the fixed value i_(MAX) (negativedetermination in step 106•8), processing returns to step 106•2, wherethe image position (X_(i+1), Y_(i+1)) is determined again for theincremented image number (i+1). This image position is a positionobtained by shifting the image from the image position (X_(i), Y_(i))determined in the pervious routine in the X direction and/or Y directionby a predetermined distance (ΔX_(i), ΔY_(i)). In the example of FIG.108, the inspection subject area is at a position (X₂, Y₂) obtained byshifting the image from (X_(i), Y_(i)) only in the Y direction, whichcorresponds to a rectangular area 108•2 b shown by a broken line.Furthermore, the values of (ΔX_(i), ΔY_(i)) (i=1, 2, . . . i_(MAX)) maybe defined as appropriate based on data of how a pattern 108•3 of thewafer inspection surface 108•1 is actually shifted empirically from thefield of view of the detector 104•7, and the number and area ofinspection subject areas.

Processing at steps 106•2 to 106•7 is carried out one after anotherrepeatedly for i_(MAX) inspection subject areas. As shown in FIG. 108,these inspection subject area are mutually shifted in position whilepartially overlapping on the wafer inspection surface 108•1 so that animage position (X_(k), Y_(k)) is obtained by making k shifts. In thisway, 16 inspection subject image data illustrated in FIG. 109 arecaptured in the image storage area 104•14. It can be understood that animage (inspection subject image) 109•1 of the acquired plurality ofinspection subject areas has partially or fully captured therein animage 109•2 of the pattern 108•3 on the wafer inspection surface 108•1.

If the incremented image number i exceeds i_(MAx) (positivedetermination in step 106•8), this subroutine is returned, andprocessing proceeds to a comparison step.

Furthermore, image data memory-transferred at step 106•6 consists of theintensity value of secondary electrons for each pixel (so called soliddata) detected by the detector 104•7, but may be stored in the storagearea 104•14 with the image data subjected various calculation processingbecause the image data is subjected to matching calculation with areference image at the subsequent comparison step (step 105•3). Suchcalculation processing includes, for example, normalization processingfor making the size and/or density of image data match the size and/ordensity of reference image data, and processing of removing as a noisean isolated group of images having a predetermined number or smallernumber of pixels. Further, instead of simple solid data, data may becompressed and converted into a feature matrix with a feature of adetection pattern extracted within the bounds of not reducing thedetection accuracy of a precise pattern. Such feature matrixes include,for example, an m×n feature matrix having as each component the total ofsecondary electron intensity values of pixels (or, normalized valueobtained by dividing the total value by the total number of pixels ofthe entire inspection subject area) included in each of m×n blocks (m<M,n<N) into which a two-dimensional inspection subject area consisting ofM×N pixels is divided. In this case, reference image data is also storedin the same form. The image data cited in the embodiments of the presentinvention includes not only mere solid data but also image datafeature-extracted with any algorithm as described above.

The flow of processing at step 105•3 will now be described according tothe flowchart of FIG. 107. First, the CPU of the control unit 104•8reads reference image data from the reference image storage unit 104•15(FIG. 104) onto a working memory of a RAM or the like (step 107•1). Thisreference image is denoted by reference numeral 109•3 in FIG. 109. Theimage number i is set to 1 (step 107•2), and inspection subject imagedata with the image number of i is read from the storage area 104•14onto the working memory (step 107•3).

Then, the read reference image data is made to match the data of theimage i to calculate a distance value D_(i) between both the data (step107•4). This distance value DU indicates similarity between thereference image and the inspection subject image i, which means that thelarger the distance value, greater the difference between the referenceimage and the inspection subject image. Any quantity indicatingsimilarity may be employed as the distance value D_(i). For example, ifimage data consists of M×N pixels, the secondary electron intensity (orfeature amount) of each pixel may be considered as each vector componentof a M×N-dimensional space, and a Euclidean distance or a coefficient ofcorrelation between a reference image vector and an image i vector onthe M×N-dimensional space may be calculated. Of course, a distance otherthan the Euclidean distance, for example, so called an urban areadistance or the like may be calculated. Further, if a large number ofpixels exist, the calculation amount considerably increases, andtherefore the distance value between image data expressed by the m×nfeature vector may be calculated as described above.

Then, whether the calculated distance value D_(i) is smaller than athreshold value Th or not is determined (step 107•5). This thresholdvalue Th is determined empirically as a reference when whether thereference image sufficiently matches the inspection subject image isdetermined. If the distance value D_(i) is smaller than thepredetermined threshold value Th (positive determination in step 107•5),it is determined that “no defect exits” on the inspection surface 1034of the wafer W (step 107•6), and this sub routine is returned. That is,if even only one of inspection subject images approximately matches thereference image, it is determined that “no defect exists”. In this way,it is not necessary that the reference image should be matched with allinspection subject images, thus making it possible to make adetermination quickly. In the example of FIG. 109, it can be understoodthat the inspection subject image of third line and third rowapproximately matches the reference image with no shift in position withrespect to the reference image.

If the distance value D_(i) is equal to or larger than the predeterminedthreshold value Th (negative determination in step 107•5), the imagenumber i is incremented by 1 (step 107•7), and whether the incrementedimage number (i+1) exceeds the fixed number i_(MAX) or not is determined(step 107•8).

If the image number i does not exceed the fixed value i_(MAX) (negativedetermination in step 107•8), processing returns to step 107•3, whereimage data is read for the incremented image number (i+1), and the sameprocessing is repeated.

If the image number i exceeds the fixed value i_(MAX) (positivedetermination in step 107•8), it is determined that “defects exit” onthe inspection surface 1034 of the wafer W (step 107•9), and this subroutine is returned. That is, if none of inspection subject imagesapproximately match the reference image, it is determined that “defectsexist”.

Each embodiment of the stage apparatus has been described above, but thepresent invention is not limited to the above examples, and may bealtered arbitrarily and appropriately within the substance of thepresent invention.

For example, the semiconductor wafer W is used as an inspection subjectsample, but the inspection subject sample of the present invention isnot limited thereto, and any sample allowing defects to be detected withan electron beam can be selected. For example, a mask or the likeprovided with a pattern for light exposure for the wafer may be used asan inspection object.

Furthermore, the present invention can be applied not only toapparatuses detecting defects using charged particle beams other thanelectrons, but also to any apparatus capable of acquiring imagesallowing defects of samples to be inspected.

Further, the deflection electrode 104•9 may be placed not only betweenthe objective lens 104•4 and the wafer W, but also at any position aslong as the area of irradiation with the primary electron beam can bechanged. For example, it may be placed between the E×B deflector 104•3and the objective lens 104•4, between the electron gun 104•1 and the E×Bdeflector 104•3, or the like. Further, by controlling a field generatedby the E×B deflector 104•3, the direction of deflection may becontrolled. That is, the E×B deflector 104•3 may also have a function asthe deflection electrode 104•9.

Furthermore, in the embodiment described above, any one of matchingbetween pixels and matching between feature vectors is performed whenperforming matching between image data, but both types of matching maybe combined. For example, compatibility between enhancement of the speedand accuracy can be achieved by two-stage processing such that first,high-speed matching is performed with feature vectors having smallcalculation amounts and as a result, for high-similarity inspectionsubject images, matching is performed with more precise pixel data.

Furthermore, in the embodiment of the present invention, a positionalshift of the inspection subject image is coped with only by shifting theposition of the area of irradiation with the primary electron beam, butprocessing of searching for an optimum matching area on image databefore or during matching processing (detecting areas of highcoefficients of correlation and performing matching between the areas)may be combined with the present invention. According to this, a largepositional shift of the inspection subject image can be coped with byshifting the position of the area of irradiation with the primaryelectron beam according to the present invention, and also a relativelysmall positional shift can be absorbed in subsequent digital imageprocessing, thus making it possible to improve the accuracy of defectdetection.

Further, the configuration in FIG. 104 has been shown as an electronbeam apparatus for defect detection, but the electro-optical system andthe like can be altered arbitrarily and appropriately. For example,electron beam irradiating means (104•1, 104•2, 104•3) of the defectinspection apparatus shown in FIG. 104 has a form such that the primaryelectron beam is made to enter the surface of the wafer W uprightly fromabove, but the E×B deflector 104•3 may be emitted, and the primaryelectron beam may be made to enter the surface of the wafer Wslantingly.

Furthermore, the flow of the flowchart of FIG. 105 is not limited to theexamples described above. For example, for a sample for which it isdetermined that defects exist at step 105•4, defect inspection in otherareas is not carried, but the flow of processing may be changed so thatdefects are detected covering all areas. Furthermore if the area ofirradiation with the primary electron beam is expanded so that almostall inspection areas of the sample can be covered with one irradiation,steps 105•7 and 105•8 may be omitted.

As described in detail above, according to the defect inspectionapparatus of this embodiment, images of a plurality of inspectionsubject areas mutually displaced while partially overlapping on thesample are each acquired, and the images of the inspection subject areasare compared with the reference image to inspect defects of the sample,thus making it possible to obtain an excellent effect such that areduction in accuracy of defect inspection resulting from a positionalshift between the inspection subject image and the reference image canbe prevented.

Further, according to the device production process of the presentinvention, defect inspection of the sample is carried out using thedefect inspection apparatus described above, thus making it possible toobtain an excellent effect such that the yield of products can beimproved and defective products can be prevented from being dispatched.

2-7-8) Device Production Process

The embodiment of a process for producing a semiconductor deviceaccording to the present invention will now be described with referenceto FIGS. 110 and 111. FIG. 110 is a flowchart showing one embodiment ofthe process for producing a semiconductor device according to thepresent invention. The production process of this embodiment includesthe following main steps.

(1) Wafer production step of producing a wafer (or wafer preparationstep of preparing a wafer) (step 110•1).

(2) Mask production step of producing a mask for use in light exposure(or mask preparation step of preparing a mask) (step 110•2).

(3) Wafer processing step of subjecting the wafer to necessary processprocessing (step 110•3)

(4) Chip assembly step of cutting out chips formed on the wafer onone-by-one basis and making the chips operable (step 1110•4).

(5) Chip inspection step of inspecting the assembled chips (step 110•5).

Furthermore, the main steps described above each consist of severalsub-steps. It is the wafer processing step (3) among these main stepsthat has decisive influences on the performance of the semiconductordevice. In this step, designed circuit patterns are stacked on the waferone after another to form a large number of chips operating as memoriesand MPUs. This wafer processing step includes the following steps.

(A) Thin film formation step of forming a dielectric thin film and awiring portion serving as an insulating layer or a thin metal filmforming an electrode portion (using CVD, spattering or the like).

(B) Oxidization step of oxidizing the thin film layer and the wafersubstrate.

(C) Lithography step of forming a resist pattern using a mask (reticle)for selectively processing the thin film layer, the wafer substrate andthe like.

(D) Etching step of processing the thin film layer and the substrateaccording to the resist pattern (e.g. using a dry etching technique).

(E) Ion/impurity injection and diffusion step.

(F) Resist peeling step.

(G) Step of inspecting the processed wafer.

Furthermore, the wafer processing step is repeated for a necessarynumber of layers to produce a semiconductor device operating asdesigned.

FIG. 111 is a flowchart showing the lithography step lying at the heartof the wafer processing step. The lithography step includes thefollowing steps.

(a) Resist coating step of coating a resist on the wafer having thecircuit pattern formed at the previous step (step 111•1).

(b) Step of exposing the resist to light (step 111•2).

(c) Development step of developing the exposed resist to obtain apattern of the resist (step 111•3).

(d) Annealing step for stabilizing the developed resist pattern (step111•4).

The semiconductor device production step, the wafer processing step andthe lithography step described above are well known, and thus are notrequired to be described further in detail.

If the defect inspection process and defect inspection apparatusaccording to the present invention are used in the inspection step (G),even a semiconductor device having a fine pattern can be inspected inhigh throughput, and therefore 100% inspection can be performed, thusmaking it possible to improve the yield of products and preventdefective products from being dispatched.

2-7-9) Inspection

Inspection procedures in the inspection step of (G) will be describedusing FIG. 112. Generally, the defect inspection apparatus usingelectron beams is expensive, and has low throughput compared to otherprocess apparatuses, and is thus used, at present, after an importantstep considered to require most strictest inspection (e.g. etching, filmformation, CMP (chemical-mechanical polishing) flatness processing,etc.), or in a more precise wiring step part, i.e. 1 to 2 steps of thewiring step and the gate wiring step as a pervious step in the case ofthe wiring step. Particularly, it is important that shape defects andelectric defects of wiring having a design rule of 100 nm or less, i.e.a line width of 100 nm or less, a via hole having a diameter of 100 nmor less and the like are found, and fed back to the process.

The wafer to be inspected is aligned on a very precise X-Y stage throughan atmosphere transportation system and a vacuum transportation system,then fixed by an electrostatic chuck mechanism or the like, and thensubjected to defect inspection according to procedures (of FIG. 112).First, the position of each die is checked and the height of each siteis detected as necessary by an optical microscope, and the results arestored. In addition thereto, the optical microscope acquires microscopicimages of areas required to be observed such as defects, and themicroscopic images are used for comparison with electron beam images.Then, the conditions of the electro-optical system are set, and theelectro beam image is used to modify information set with the opticalmicroscope to improve the accuracy.

Then, information of a recipe appropriate to the type of wafer(immediately preceding step, whether the wafer size is 200 mm or 300 mm,and the like) is inputted to the apparatus, followed by setting theinspection site, the electro-optical system, inspection conditions andthe like, and then defect inspection is carried out usually in real timewhile acquiring an image. Comparison between cells and die comparisonare carried out by a high-speed information processing system havingalgorithms, and the results are outputted to a CRT and the like andstored in a memory as necessary.

Defects include particle defects, shape abnormalities (pattern defects)and electric defects (breakage and poor conduction of wiring or vias,etc.), and these defects can be identified, and defects can beautomatically classified in real time on the basis of the size of thedefect and whether or not the defect is a killer defect (serious defectresulting in an unusable chip, etc.). Particularly, the process iseffective in classifying the defects of wiring having a line width of100 nm or less, a via having a diameter of 100 nm or less and the like.Detection of electric defects is achieved by detecting a contrastabnormality. For example, the site of poor conduction is usually chargedpositively and has a contrast reduced by irradiation with the electronbeam (about 500 eV), and thus can be differentiated from a normal site.The electron beam irradiating means in this case refers to low-potential(energy) electron beam generating means (generation of thermalelectrons, UV/photoelectrons) provided for clarifying the contrast bythe difference in potential, aside from electron beam irradiating meansfor usual inspection. Before irradiating the electron beam forinspection to the inspection object area, this low-potential electronbeam (having energy of 100 eV or less, for example) isgenerated/applied. In the case of the projection system in which theinspection site can be positively charged only by irradiating anelectron beam for inspection, it is not necessary to provide separatelylow-potential electron beam generating means depending onspecifications. Furthermore, defect inspection can be carried out usinga difference in contrast caused by application of a positive or negativepotential to a sample such as a wafer with respect to the referencepotential or the like (caused by a difference in flowability dependingon the forward direction or inverse direction of the element).

The contrast by a difference in potential may be converted into an imageof a signal effective for displaying potential contrast data and thendisplayed. The potential contrast image can be analyzed to identify astructure at a voltage higher or lower than an expected value, i.e. poorinsulation or poor conduction and defects. For example, potentialcontrast images are acquired from different dies on the wafer,respectively, and differences between the images are detected torecognize defects. Furthermore, image data equivalent to the potentialcontrast image of the inspection subject die is generated from designdata such as CAD data, and a difference between this image data and thepotential contrast image acquired from the inspection subject die on thewafer is detected to recognize defects.

The process can be used in a line width measurement apparatus andmeasurement of matching accuracy. Information of the wafer to beinspected, for example the number of the cassette and the number of thewafer (or lot number) is all stored and managed as to the currentposition and sate of the wafer. Thus, there arises no trouble oferroneously performing inspection twice or performing no inspection.

2-8) Inspection Process

2-8-1) Overview

The basic flow of inspection is shown in FIG. 113. First, aftertransportation of the wafer including an alignment operation 113•1, arecipe specifying conditions and the like related inspection (113•2). Atleast one recipe are required for the inspection subject wafer, but aplurality of recipes may exist for one inspection subject recipe forcoping with a plurality of inspection conditions. Furthermore, if thereare a plurality of wafers having the same pattern, the plurality ofwafers may be inspected with one recipe. A path 113•3 of FIG. 113indicates that creation of the recipe is not required immediately beforethe inspection operation if inspection is carried out with a recipecreated in the past in this way. Subsequently, in FIG. 113, aninspection operation 113•4 carries out inspection according toconditions and sequences described in the recipe. Defect extraction iscarried out immediately each time a defect is found during theinspection operation, and the following operations are carried outalmost in parallel:

a) operation of classifying defects (113•5) and adding extracted defectinformation and defect classification information to a result outputfile;

b) operation of adding an extracted defect image to an image dedicatedresult output file or file; and

c) operation of displaying defect information such as a position of anextracted defect on an operation screen.

When inspection is completed for each inspection subject wafer, thefollowing operations are carried out almost in parallel:

a) operation of closing and storing the result output file;

b) operation of sending the inspection result if the inspection resultis requested by external communication; and

c) operation of discharging the wafer.

If a setting for continuously inspecting wafers is made, a nextinspection subject wafer is conveyed, and the series of operationsdescribed above are repeated.

The flow of FIG. 113 will be described further in detail below.

(1) Creation of Recipe

The recipe is a set file for conditions and the like relating toinspection, and can be stored. The recipe is used to make a setting ofapparatus during inspection or before inspection, the conditionsrelating to inspection described in the recipe are as follows:

a) inspection object dies;

b) inspection areas within die;

c) inspection algorithm;

d) detection conditions (conditions necessary for defect extraction suchas inspection sensitivity); and

e) observation conditions (conditions necessary for observation such asmagnification, lens voltage, stage speed and inspection order), c)inspection algorithm will be described specifically later.

For the setting of inspection object die among these conditions, theoperator designates dies to be inspected with respect to a die mapscreen displayed on the operation screen as shown in FIG. 114. In theexample of FIG. 114, a die 1 on the end face of the wafer and a die 2judged as an apparently defective die 2 in the previously step aregrayed out and omitted from the inspection object, and remaining diesare defined as inspection object dies. Furthermore, a function ofautomatically designating inspection dies based on a distance from theend face of the wafer and pass/fail information of dies detected in theprevious step is also provided.

Furthermore, to set inspection areas within the die, the operatordesignates inspection areas with an input device such as a mouse basedon images acquired with an optical microscope or EB microscope, withrespect to an in-die inspection area setting screen displayed on theoperation screen, as shown in FIG. 115. In the example of FIG. 115, anarea 115•1 indicated by a solid line and an area 115•2 indicated by abroken line are set.

The area 115•1 has almost an entire area of the die as a set area. Anadjacent die comparison method (die-die inspection) is used as theinspection algorithm, and the details of detection conditions andobservation conditions for this area are set separately. For the area115•2, array inspection (inspection) is used as the inspectionalgorithm, and the details of detection conditions and observationconditions are set separately. That is, a plurality of inspection areascan be set, and a unique inspection algorithm and inspection sensitivitycan be set for each inspection area. Furthermore, one inspection areacan be superimposed on the other, and the same area can be processedwith different inspection algorithms at a time.

(2) Inspection Operation

For inspection, the inspection subject wafer is finely divided intocertain scan widths and scanned as shown in FIG. 116. The scan widthapproximately depends on the length of a line sensor, but the endportions of line sensors slightly overlap one another. This is for thepurpose of evaluating continuity between lines when detected defects arefinally subjected to integration processing, and providing allowance foralignment of images when comparison inspection is carried out. Theoverlap amount thereof is about 16 dots for the line sensor of 2048dots.

The scan direction and sequence are schematically shown in FIG. 117.That is, a two-way operation A for reduction of inspection time, aone-way operation B due to mechanical limitation, or the like can beselected by the operator.

Furthermore, a function of automatically calculating an operation forreducing the scan amount based on the setting of inspection object diesin the recipe to carry out inspection is also provided. FIG. 118-1 showsan example of scanning where there is one inspection die 118•1, in whichunnecessary scans are not performed.

2-8-2) Inspection Algorithm

Algorithms of inspection carried out by this apparatus are classifiedbroadly into the following two types:

1. array inspection (cell inspection); and

2. random inspection (die inspection).

As shown in FIG. 118-2, the die is separated into a cell portion 118•2having a cycle structure that is used mainly for a memory, and a randomportion 118•3 having no cycle structure. The cell portion 118•2 having acycle structure is capable of being inspected by comparison betweencells in the same die because a plurality of comparative objects existin the same die. On the other hand, the random portion 118•3 requirescomparison between dies because there is no comparative object in thesame die.Random inspection is further classified as follows according tocomparative objects:

a) adjacent die comparison method (Die-Die inspection);

b) reference die comparison method (die-Any Die inspection); and

c) CAD data comparison method (Cad Data-Any Die inspection).

A method generally called as a golden template method refers to themethods b) and c), and the reference die is a golden template on thereference die comparison method, while CAD data is a golden template inthe CAD data comparison method.

The operation of each algorithm will be described below.

2-8-2-1) Array Inspection (Cell Inspection)

Array inspection is applied for inspection of the cycle structure A DRAMcell or the like is one example thereof.

For inspection, a reference image as a reference is compared with aninspection subject image, and a difference thereof is extracted as adefect. The reference image and the inspection subject image may bebinary images or multi-value images for improvement of detectionaccuracy.

The defect may be the difference itself between the reference image andthe inspection subject image, but a secondary determination forprevention of erroneous detection may be made based on differenceinformation such as the amount of detected difference and the total areaof images having the difference.

In array inspection, the reference image is compared with the inspectionsubject image in a structure cycle unit. That is, images collectivelyacquired with the CCD or the like may be compared in one structure cycleunit while reading the images, or if the reference image has u structurecycle units, n structure cycle units may be compared at a time.

One example of a method for generating a reference image is shown inFIG. 119. Here, an example of comparison in one structure cycle unit isdescribed, and thus generation of one structure cycle unit is shown. Thenumber of cycles can be set to n in the same method.

As a premise, the inspection direction is a direction A in FIG. 119.Furthermore, a cycle 4 is an inspection subject cycle. The magnitude ofthe cycle is inputted by the operator watching the image, and thereforecycles 1 to 6 can easily be recognized in FIG. 119.

A reference cycle image is generated by adding cycles 1 to 3 immediatelybefore the inspection subject cycle in each pixel. Even if defects existin any of cycles 1 to 3, influences thereof are not significant becauseequalization processing is performed. This generated reference cycleimage is compared with an inspection subject cycle image 4 to extractdefects

When an inspection subject cycle image 5 is then inspected, cycles 2 to4 are added and averaged to generate a reference cycle image.Subsequently, an inspection subject cycle image is similarly generatedfrom images obtained before acquirement of the inspection subject cycleimage to continue inspection.

2-8-2-2) Random Inspection (Die Inspection)

Random inspection can be applied without being limited by the structureof the die. For inspection, a reference image as a reference is comparedwith an inspection subject image, and a difference thereof is extractedas a defect. The reference image and the inspection subject image may bebinary images or multi-value images for improvement of detectionaccuracy. The defect may be the difference itself between the referenceimage and the inspection subject image, but a secondary determinationfor prevention of erroneous detection may be made based on differenceinformation such as the amount of detected difference and the total areaof images having the difference. Random inspection can be classifiedbased on how the reference image is determined. The operation will bedescribed below.

A. Adjacent Die Comparison Method (Die-Die Inspection)

A reference image is a die adjacent to an inspection subject die. Theinspection subject image is compared with two dies adjacent thereto tomake a determination on defects. That is, in FIGS. 120 and 121, themethod has the following steps in a situation in which a switch 121•4and a switch 121•5 are set so that a memory 121•1 and a memory 121•2 ofan image processing apparatus are connected to a path 121•41 from acamera 121•3:

a) step of storing a die image 1 in the memory 121•1 from the path121•41 along a scan direction S;

b) step of storing a die image 2 in the memory 121•2 from the path121•41;

c) acquiring the die image 2 from the path 121•42 while carrying out thestep b), and at the same time comparing the acquired die image 2 withimage data stored in the memory 121•1, having the same relative positionin the die, to determine a difference;

d) step of storing the difference determined in the step c);

e) step of storing a die image 3 in the memory 121•1 from the path121•41;

f) acquiring the die image 3 from the path 121•42 while carrying out thestep c), and at the same time comparing the acquired die image 3 withimage data stored in the memory 121•1, having the same relative positionin the die, to determine a difference;

g) step of storing the difference determined in the step f);

h) step of making a determination on defects of the die image 2 from theresults stored in the steps d) and g); and

i) step of repeating steps a) to h) in subsequent continuous dies.

By setting, before determining the difference in steps c) and f),position alignment of compared two images by setting: correction that iscarried out so that a difference in position is eliminated; or densityalignment; correction that is carried out so that a difference indensity is eliminated; or both position alignment and density alignmentmay be performed.

B. Reference Die Comparison Method (Die-any Die Inspection)

A reference die is designated by the operator. The reference die is adie existing on the wafer, or a die image stored before inspection, andthe reference die is first scanned or transferred, and the image isstored in a memory as a reference image. That is, in FIGS. 121 and 122,the method has the following steps:

a) step of selecting a reference die from dies of the inspection subjectwafer or die images stored before inspection by the operator;

b) step of setting the switch 121•4 and the switch 121•5 so that atleast one of the memory 121•1 and the memory 121•2 of the imageprocessing apparatus are connected to the path 121•41 from the camera121•3, if the reference die exists on the inspection subject wafer;c) step of setting the switch 121•4 and the switch 121•5 so that atleast one of the memory 121•1 and the memory 121•2 of the imageprocessing apparatus are connected to a path 121•7 from a memory 121•6having a reference image as a die image stored therein, if the referencedie is a die image stored before inspection;d) step of scanning the reference die and transferring the referenceimage as a reference die image to the memory of the image processingapparatus, if the reference die exists on the inspection subject wafer;e) step of transferring the reference image as a reference die image tothe memory of the image processing apparatus without necessity toperform scanning, if the reference die is a die image stored beforeinspection;f) step of comparing an image obtained by sequentially scanning theinspection subject image, the image in the memory to which the referenceimage as a reference die image is transferred, and image data having thesame relative position in the die to determine a difference;g) step of making a determination defects from the difference obtainedat step f); andh) step of inspecting the same area with respect to the scan position ofthe reference die and the die origin of the inspection subject die forthe entire wafer continuously as shown in FIG. 124, and repeating thesteps d) to g) while changing the scan position of the reference dieuntil the entire die is inspected.

By setting, before determining the difference in step f), positionalignment of compared two images by setting: correction that is carriedout so that a difference in position is eliminated; or densityalignment: correction that is carried out so that a difference indensity is eliminated; or both position alignment and density alignmentmay be performed.

The reference die image stored in the memory of the image processingapparatus at the step d) or e) may be the entire reference die, or maybe inspected while being updated as part of the reference die.

C. CAD Data Comparison Method (CAD Data-any Die Inspection)

In the step of production of a semiconductor shown in FIG. 123, acomparison image is created from CAD data being an output of a step ofdesigning a semiconductor pattern with CAD and the comparison image isdefined as a reference image. The reference image may be an image of theentire die or part of the die including an inspection area.

Furthermore, the CAD data is usually vector data, and cannot be used asa comparison image unless the data is converted into raster dataequivalent to image data equivalent to image data obtained by a scanningoperation. In this way, the following conversions are carried out forCAD data processing work.

a) Vector data being CAD data is converted into raster data.

b) The conversion a) is carried out in a unit of image scan widthobtained by scanning the inspection subject die during inspection.

c) The conversion b) converts an image to be obtained by scanning theinspection subject die and image data having the same relative positionin the die.

d) The conversion c) is carried out with inspection scanning andconversion work overlapping one another.

The conversions a) to d) are examples of conversion in an unit of imagescan width for enhancement of the speed, but scanning can be performedeven if the conversion unit is not fixed to the image scan width.Furthermore, the method has at least one of the following functions asan additional function for work of converting vector data into rasterdata:

a) function of processing raster data into a multiple value;

b) function of setting a gray scale weight and an offset in theprocessing into a multiple value in view of the sensitivity of theinspection apparatus with respect to the function a); and

c) function of carrying out image processing for subjecting pixels toprocessing such as expansion and contraction after converting vectordata into raster data.

In FIG. 121, inspection steps by the CAD data comparison method are asfollows:

a) step of converting CAD data into raster data with a calculator 1, andgenerating a comparison image with the additional function and storingthe comparison image in the memory 121•6;

b) step of setting the switch 121•4 and the switch 121•5 so that atleast one of the memory 121•1 and the memory 121•2 of the imageprocessing apparatus are connected to the path 121•7 from the memory121•6;

c) step of transferring the comparison image of the memory 121•6 to thememory of the image processing apparatus;

d) step of comparing an image obtained by sequentially scanning theinspection subject image, the image in the memory to which thecomparison image is transferred, and image data having the same relativeposition in the die to determine a difference;

e) step of making a determination defects from the difference obtainedat step d); and f) step of inspecting the same area of the inspectionsubject die over the entire wafer with the scan position of thereference die as a comparison image continuously as shown in FIG. 124,and repeating steps a) to e) while changing the scan position of thereference die until the entire die is inspected.

By setting, before determining the difference in step d), positionalignment of compared two images by setting: correction that is carriedout so that a difference in position is eliminated; or densityalignment: correction that is carried out so that a difference indensity is eliminated; or both position alignment and density alignmentmay be performed.

The reference die image stored in the memory of the image processingapparatus at step c) may be the entire reference die, or may beinspected while being updated as part of the reference die.

2-8-2-2′) Method for Carrying Out Cell Inspection and Die Inspection atthe Same Time

The algorithms of array inspection (cell inspection) and randominspection for inspecting the cycle structure have been described, butcell inspection and die inspection can be carried out at the same time.Specifically, the cell portion and the random portion are processedseparately, and a comparison is made between cells in the die for thecell portion, while a comparison with an adjacent die, the reference dieor CAD data is made for the random portion. This allows inspection timeto be considerably reduced, resulting in an improvement in throughput.

Furthermore, in this case, it is preferable that inspection circuits ofthe cell portion are individually independently provided. Furthermore,if inspection is not carried out at the same time, it is also possibleto provide one inspection circuit, wherein a setting is made so that theswitch can be made between software for cell inspection and randominspection, and comparison inspection is carried out by switching ofsoftware. That is, if inspection of a pattern is carried out usingalgorithms for a plurality of operations, different circuits may beprepared for the algorithms to carry out inspection at a time, oralgorithms matching those operations may be provided to carry outinspection with the switch made between the algorithms with one circuit.In any case, the present invention can be applied even if the type ofthe cell portion is complicate, and a comparison is made between cellsfor this type of cell portion, and a comparison is made between dies orbetween the die and CAD data for the random portion.

2-8-2-3) Focus Mapping

The basic flow of a focus function is shown in FIG. 125. First, aftertransportation of the wafer including the alignment operation, a recipespecifying conditions and the like relating to inspection is created.There is a focus map recipe as one of such recipes, and auto-focusing isperformed during the inspection operation and the review operationaccording to focus information specified in the recipe. Procedures forcreating the focus map recipe and operational procedures ofauto-focusing will be described below.

Procedures for Creating Focus Map Recipe

The focus map recipe has an independent input screen in this example,and the operator carries out the following steps to create the recipe,but the recipe may be added to an input screen provided for a differentpurpose.

a) Step of inputting focus map coordinates such as a die position inwhich a focus value is inputted, and a pattern in the die. Switch 126•1in FIG. 126.

b) Step of setting a die pattern required when the focus value isautomatically measured. This step may be skipped if the focus value isnot automatically measured.

c) Step of setting the best focus value of the focus map coordinatesdetermined at step a).

At step a), the operator may designate any die, but all dies may beselected, or dies may be selected for every n dies. Furthermore, in theinput screen, the operator may select either a diagram schematicallyshowing a die arrangement or an image using a real image.

At step c), a selection/setting is made in a mode in which the operatormanually sets a value with a focus switch 126•2 associated with thevoltage value of an electrode for focusing (switch 126•3 in FIG. 126) ora mode in which the focus value is automatically determined (switch126-4 in FIG. 126).

Procedures for automatically measuring a focus value

In FIG. 127, for example, the procedures for automatically determining afocus value at step c) include:

a) obtaining an image of focus position Z=1 and calculating a contrastthereof;

b) carrying out the procedure a) for Z=2, 3, 4.

c) determining a contrast function with regression from the contrastvalues obtained in the procedures a) and b) (FIG. 127); and

d) calculating Z providing a maximum value of the contrast function andsetting the maximum value to the best focus value.

For example, the die pattern required when the focus value isautomatically measured shows a good result if a line & space shown inFIG. 128 is selected, but the contrast can be measured irrespective ofthe shape as long as a black-and-white pattern is provided.

By carrying out the procedures a) to d), the best focus value of onepoint is determined. The data format at this time is (X, Y, Z), whereinXY is coordinates with which the focus is determined, Z is a set of thebest focus value, and the focus map coordinate number (X, Y, Z)determined with the focus map recipe exists. This is called a focus mapfile as part of the focus map recipe.

Operational Procedures of Auto-Focusing

The method for setting the focus to the best focus during the inspectionoperation of acquiring images from the focus map recipe and the reviewoperation comprises the following steps.

a) Position information is subdivided based on a focus map file 1created during creation of the focus map recipe, the best focus at thistime is calculated, and a subdivided focus map file 2 is created;

b) The calculation of step a) is performed with an interpolationfunction;

c) The interpolation function of step b) is linear interpolation, splineinterpolation or the like, which is designated by the operator duringcreation of the focus map recipe.

d) The XY position of the stage is monitored to change the voltage ofthe electrode for focusing to a focus value suitable for the current XYposition, described in the focus map file 2.

To describe the procedures more specifically, in FIG. 129, the blackcircle corresponds to focus values of the focus map file 1, and thewhite circle corresponds to focus values of the focus map file 2,wherein

1. intervals between focus values of the focus map file are interpolatedwith focus values of the focus map file, and

2. the focus position Z is changed according to scanning to maintain thebest focus value and at this time, for the interval between focus mapfiles (white circles), a value is retained up to a position at which thevalue is changed.

2-8-2-4) Litho-Margin Measurement

Embodiments relating to litho-margin measurement will be describedbelow.

(1) Embodiment 10 Litho-Margin Measurement 1

Overview

1. The range of conditions for a light-exposure machine and bestconditions are determined. The target is the focus.

2. This embodiment is a method of application of inspection apparatus,and is not limited to the electron beam mapping method and the scanningmethod. That is, the method using light, the electron beam method, andany combination of such methods with the mapping method or scanningmethod may be used.3. Application of reference die comparison method (Die-Any Dieinspection)

FIG. 130 shows a flow showing the operation of the embodiment 1. Theembodiment will be described based on this figure.

At step 130•1, conditions are changed to two dimensionally expose thesurface of the wafer to light using focus conditions and exposure timeconditions as parameters as shown in FIG. 131 as an example.Furthermore, an image pattern of one shot=1 die is used.

Many stepper light-exposure machines have a function of automaticallychanging the parameter to perform light-exposure, generally called TESTexposure, and this function may be used directly.

At step 130•2, steps of development resist peeling, etching, CVD, CMP,plating and the like may be carried out, and particularly in observationwith the electron beam, the resist is charged and is thus hard to beobserved, and therefore steps of development, resist peeling and platingare carried out. Resist observation is desirable.

Details of step 130•3 will be described with FIG. 132. In this step,using a function of measuring a contrast of an image set by the operatorof the inspection apparatus carrying out step 130•4, the minimum line &space portion of the die pattern is recorded as an area where thecontrast is measured, and the following work is conducted.

First, an upper limit Db and a lower limit Da of exposure time aredetermined. For exposure time equal to or greater than Db and exposuretime equal to or less than Da, the contrast value is extremely low, andthus such exposure time is excluded from inspection (grayed-out part inFIG. 132).

Then, an upper limit Fb and a lower limit Fa of the focus value aredetermined. For any focus value equal to or greater than Fb and anyfocus value equal to or smaller than Fa, the contrast value is extremelylow, and thus such focus values are excluded from inspection (grayed-outpart in FIG. 133).

Then, a die at intersection of a row of dies Ds in the middle between Daand Db and a row of dies Fs in the middle between Fa and Fb is selectedas a best exposure condition shot. The step of selecting the bestexposure condition shot is all carried out automatically.

At step 130•4, inspection is carried out by the reference die comparisonmethod (Die-Any Sie inspection) with the reference die as a comparisonimage and with white dies as inspection subject dies in FIG. 132.

At step 130•5, a determination is made on exposure conditions using theinspection result in step 130•4. That is, an effect is used such that ifexposure conditions are not appropriate, for example, the line and spaceof the die pattern are not resolved, or the edge portion of the patternhas an obtuse angle, so a difference occurs between the reference imageand the inspection subject image, resulting in detection as patterndefects. Of course, pattern defects and particles caused by erroneousexposure, not caused by exposure conditions, may be detected, but inthis case, inspection is carried out again. However, the frequency ofoccurrence of such a case is so low in terms of probability that noproblem arises.

Specific procedures of the step 130•5 are as follows.

1) Because higher priority is given to determination of a focus margin,exposure time is fixed at Ds in FIG. 132, and a relation between thefocus value and the number of defects is determined (FIG. 133).

2) At this time, the criterion for determination on the focus value issuch that no defect occurs due to exposure conditions, and thereforefocus values acceptable as exposure conditions are values in the rangeof F1 to F2 as a conclusion.

3) For the type of value/unit of expression in the light-exposuremachine which F1 and F2 specifically have, it can be easily calculatedby transferring the position of the die and its exposure conditionsthrough a communication path connected from the light-exposure machinevia RS232C or Ethernet. The apparatus has a function of converting thevalue into a value capable of being directly inputted to the exposuremachine and displaying together with a function of pass/faildetermination as exposure conditions.4) Furthermore, if a dedicated communication path or a communicationpath of SEMI standard or the like is used, the result by this inspectionapparatus can be fed back to the light-exposure machine. The aboveprocedures are further carried out with exposure conditions (exposuretime) changed to determine the margin of focus and exposure.

(2) Embodiment 11 Litho-Margin Measurement 2

Overview

The range of conditions for a light-exposure machine and best conditionsare determined. The target is the focus.

1. This embodiment is a method of application of inspection apparatus,and is not limited to the electron beam mapping method and the scanningmethod. The optical method, the electron beam method, and combinationsof such methods with the mapping method or scanning method may be used.2. Application of CAD data comparison method (CAD Data-Any Dieinspection)

FIG. 134 shows a flow showing the operation of the embodiment 2. Theembodiment will be described based on this figure.

At step 134•1, conditions are changed to two dimensionally expose thesurface of the wafer to light using focus conditions and exposure timeconditions as parameters as shown in FIG. 135 as an example.Furthermore, an image pattern of one shot=1 die is used.

Many stepper light-exposure machines have a function of automaticallychanging the parameter to perform light-exposure, generally called TESTexposure, and this function may be used directly.

At step 134•2, steps of development, resist peeling, etching. CVD, CMP,plating and the like may be carried out, and particularly in observationwith the electron beam, the resist is charged and is thus hard to beobserved, and therefore steps of development, resist peeling and platingare carried out. Preferably, the step is ended with observation at thelevel of the resist.

At step 134•3, a reference image required to have best conditions wherepossible is generated from CAD data having an exposed shot pattern. Atthis time, raster data as image data is processed into a multiple value.As shown in FIG. 136, in patterns having different line widths, forexample a pattern A, a pattern B and a pattern C, the pattern C is finerthan the pattern B, but when a comparison is made for the level of whiteof the pattern empirically, the level of white of the pattern C iscloser to black than that of the pattern B, and when a comparison ismade for the level of black of the pattern, the level of black of thepattern C is closer to white than that of the pattern B. Thus, imagedata is processed into a multiple value in consideration of not just twovalues, one appearing black and the other appearing white as an image,but the shape and fineness of the pattern, the pattern position on thewafer and the like.

Furthermore, in consideration of setting conditions of the observationsystem and influences of charge-up, magnetic fields and the like at thesame time, image data generated from CAD data is subjected to imageprocessing such that a difference is not recognized as pseudo defectswhen an image obtained by actual observation is compared with image datagenerated from CAD data.

At step 134•4, the image generated at step 134•3 is defined as acomparison image, dies on the wafer are defined as inspection subjectimages, and die comparisons are made to carry out inspection.

At step 134•5, a determination is made on exposure conditions using theinspection result at step 134•4. That is, an effect is used such that ifexposure conditions are not appropriate, for example, the line and spaceof the die pattern are not resolved, or the edge portion of the patternhas an obtuse angle, so a difference occurs between the reference imageand the inspection subject image, resulting in detection as patterndefects. Of course, pattern defects and particles caused by erroneousexposure, not caused by exposure conditions, may be detected, but inthis case, inspection is carried out again. However, the frequency ofoccurrence of such a case is so low in terms of probability that noproblem arises.

Specific procedures of the step 134•5 are as follows.

1) Because higher priority is given to determination of a focus margin,exposure time is set to an empirically obtained fixed value, and arelation between the focus value and the number of defects in this caseis determined (FIG. 137).

2) At this time, the criterion for determination on the focus value issuch that no defect occurs due to exposure conditions, and thereforefocus values acceptable as exposure conditions are values in the rangeof F1 to F2 as a conclusion.

3) For the type of value/unit of expression in the light-exposuremachine which F1 and F2 specifically have, it can be easily calculatedby transferring the position of the die and its exposure conditionsthrough a communication path connected from the light-exposure machinevia RS232C or Ethernet. The apparatus has a function of converting thevalue into a value capable of being directly inputted to the exposuremachine and displaying together with a function of pass/faildetermination as exposure conditions.4) Furthermore, if a dedicated communication path or a communicationpath of SEMI standard or the like is used, the result by this inspectionapparatus can be fed back to the light-exposure machine.

The litho-margin measurement of exposure conditions has been describedabove, a reticle or stencil mask as a mask for exposure may beinspected. In this case, inspection for determination of exposureconditions can be simplified.

3. Other Embodiments 3-1) Alteration Example of Stage Apparatus

FIG. 138 shows one alteration example of stage apparatus in a detectionapparatus of the present invention.

A partition plate 138•4 largely protruding almost horizontally in the +Ydirection and −Y direction (lateral direction in FIG. 139) is mounted onthe upper face of a Y direction movable portion 138•2 of a stage 138•1,and a diaphragm portion 138•5 having a small conductance is alwaysformed between the partition plate 138•4 and the upper face of an Xdirection movable portion 138•4. Furthermore, a similar partition plate138•6 is formed on the upper face of the X direction movable portion138•4 in such a manner as to protrude in the ±X direction (lateraldirection in (A) of FIG. 138), and a diaphragm portion 138•8 is alwaysformed between the partition plate 138•6 and the upper face of a stagetable 138•7. The stage table 138•7 is fixed on the bottom wall in ahousing 138•9 by a well known method

Accordingly, the diaphragm portions 138•5 and 138•8 are always formedirrespective of the position to which a sample table 138•10 moves, andtherefore if gas is emitted from guide surfaces 138•11 and 138•12 whenthe movable portions 138•2 and 138•4 move, movement of emitted gas isprevented by the diaphragms 138•5 and 138•8, thus making it possible toconsiderably reduce an increase in pressure of a space 138•13 near thesample to which a charged beam is applied.

Grooves for differential exhaust shown in FIG. 140 are formed around astatic pressure bearing 138•14 on the side face and lower face of themovable portion 138•2 of the stage and the lower face of the movableportion 138•4, and the apparatus is evacuated through the grooves, andtherefore if the diaphragm portions 138•5 and 138•8 are formed, emittedgas from the guide surface is mainly discharged by the differentialexhaust portions. Accordingly, the pressures of spaces 138•15 and 138.16within the stage are higher than the pressure within a chamber C. Thus,by additionally providing sites to be evacuated not just evacuating thespaces 138•15 and 138•16 through differential exhaust grooves 140•1 and40•2, the pressures of the spaces 138•15 and 138•16 can be reduced, andan increase in pressure of the space 138•13 near the sample can bereduced to a lower level. Evacuation channels 138•17 and 138•18 for thispurpose are provided. The evacuation channel extends through the stagetable 138•7 and the housing 138•9 to outside a housing 138•9.Furthermore, the evacuation channel 138•18 is formed in the X directionmovable portion 138•4, and extends through the lower face of the Xdirection movable portion 138•4.

Furthermore, if the partition plates 138•3 and 138•6 are placed, thechamber should be upsized so that the chamber and the partition plate donot interfere with each other, but this can be improved by employing aflexible material or structure for the partition plate. In thisembodiment, it can be considered that the partition plate is formed by arubber or formed into a bellow shape, and the end portion in thetraveling direction is fixed to the X direction movable portion 138•4for the partition plate 138•3, and fixed to the inner wall of thehousing 138•9 for the partition plate 138•6. Furthermore, referencenumeral 138•19 denotes a column.

FIG. 141 shows a second alteration example of stage apparatus. In thisaspect, a cylindrical partition 141•2 is formed around the end portionof a column or a charged beam irradiating portion 141•1 so that adiaphragm is provided between the partition and the upper face of asample W. In this configuration, even if gas is emitted from the XYstage to increase the pressure within the C chamber, a space 141•3inside the partition is partitioned by the partition 141•2 and evacuatedthrough a vacuum tube 141•4, and therefore a difference in pressure isproduced between the space within the chamber C and the space 141•3inside the partition, so that the increase in pressure of the space141•3 inside the partition can be reduced to a low level. The size of agap between the partition 141•2 and the surface of the sample depends onthe level at which the pressures within the chamber C and around theirradiation area 141•1 are kept, but is appropriately several tens of μmto several mm. Furthermore, the partition 141•2 is made to communicatewith the vacuum tube by a well known method.

Furthermore, in a charged beam irradiation apparatus, there are caseswhere a high voltage of about several kilovolts is applied to the sampleW, and a discharge may be caused if a conductive material is placed nearthe sample. In this case, if an insulating material such as ceramics isused for the material of the partition 141-2, no discharge is causedbetween the sample W and the partition 141•2.

Furthermore, a ring member 141•5 placed around the sample W (wafer) is aplaty adjustment part fixed on a sample table 141•6, and is adjusted tohave a height equal to that of the wafer so that very small gaps 141•7are formed over the entire circumference of the leading end portion ofthe partition 141•2 even if a charged beam is applied to a sample suchas a wafer. Consequently, irrespective of the position of the wafer W towhich the charged beam is applied, constant very small gaps 952 arealways formed at the leading end portion of the partition 141•2, thusmaking it possible to stably keep the pressure of the space 141•3 aroundthe leading end portion of the column.

Another alteration example is shown in FIG. 142. A partition 142•1including a differential exhaust structure is provided around thecharged beam irradiating portion 141•2 of the column 138•19. Thepartition 142•1 has a cylindrical shape, a circular groove 142•2 isformed therein, and an evacuation channel 142•3 extends upward from thecircular groove. The evacuation channel is connected to a vacuum tube142•5 via an internal space 142•4. A very small gap of about severaltens of μm to several mm is formed between the lower end of thepartition 142•1 and the upper face of the sample W.

In this configuration, even if gas is emitted from with movement of thestage to increase the pressure within the chamber C, and the gas flowsinto the leading end portion or charged beam irradiating portion 141•2,the partition 142•1 reduces the gap between itself and the sample W toconsiderably diminish the conductance, so that the gas is hindered fromflowing into the leading end portion and thus the amount of inflow isreduced. Further, the gas flowing into the portion is exhausted from thecircular groove 142•2 to the vacuum lube 142•5, and thus little gasflows into a space 141•6 around the charged beam irradiating portion141•2, thins making it possible to keep the pressure in the charged beamirradiating portion 141•2 at a desired vacuum.

Still another alteration example is shown in FIG. 143, a partition 143•1is provided around the chamber C and the charged beam irradiatingportion 141•1 to isolate the charged beam irradiating portion 141•1 fromthe chamber C. The partition 143•1 is coupled to a freezer 143•3 via asupport member 143•2 made of material having a high thermal conductivitysuch as copper or aluminum, and is cooled to about −10° C. to −200° C. Amember 143•4 is intended for hindering thermal conduction between thecooled partition 143•1 and the column 138•19, and is made of materialhaving a low thermal conductivity such as ceramics or resin material.Furthermore, a member 143•5 is made of non-insulating material such asceramics, and is formed at the lower end of the partition 143•1 toprevent the sample W and the partition 143•1 from causing a discharge.

Owing to this configuration, gas molecules flowing from the chamber intothe charged beam irradiating portion is hindered from flowing into thecharged beam irradiating portion by the partition 143-1, or frozen andcollected on the surface of the partition 143•1 even if they flow intothe portion, thus making it possible to keep the pressure of the chargedbeam irradiating portion 143•6 at low level.

Furthermore, for the freezer, various freezers such as cooling withliquid nitrogen, a He freezer and a pulse tube-type freezer may be used.

Still another alteration example is shown in FIG. 144. Partition plates144•1 and 144•2 are provided on both the movable portions of the stageas in the case of the configuration shown in FIG. 138, and a space 144•4and the chamber C are partitioned via diaphragms 144•5 and 144•6 bythese partitions even if a sample table 144•3 moves to any position.Further, a partition 144•7 similar to that shown in FIG. 141 is formedaround the charged beam irradiating portion 141•1, and the chamber C anda space including the charged beam irradiating portion 141•1 arepartitioned via a diaphragm 144•8. Thus, even if gas adsorbed on thestage is emitted into the space 144•4 to increase the pressure of thisarea during movement of the stage, an increase in pressure of thechamber C is reduced to a low level, and an increase in pressure of aspace 144•9 is reduced to a lower level. Consequently, the pressure ofthe charged beam irradiation space 144•9 can be kept at a low level.Furthermore, the partition 142•1 including a differential exhaustmechanism as shown in the partition 144•7 is used, or a partition cooledby a freezer as shown in FIG. 142 is used, whereby the space 144•9 canbe stably kept at a lower pressure.

According to these embodiments, the following effects can be exhibited.

(1) The stage apparatus can exhibit a accurate positioning performanceunder vacuum, and the pressure at the charged beam irradiation positionis hard to increase. That is, the sample can be accurately processedwith a charged beam.

(2) Gas emitted from the static-pressure bearing support portion canhardly pass through the partition to the charged beam irradiation areaside. In this way, the vacuum at the charged beam irradiation positioncan be further stabilized.

(3) Emitted gas is hard to pass to the charged beam irradiation areaside, and thus the vacuum in the charged beam irradiation area can beeasily maintained with stability.

(4) The inside of the vacuum chamber is divided into a charged beamirradiation chamber, a static-pressure bearing chamber and anintermediate chamber via a small conductance. A vacuum pumping system isformed such that the charged beam irradiation chamber, the intermediatechamber and the static-pressure bearing chamber are arranged inascending order of pressure. Variations in pressure in the intermediatechamber are further reduced, and variations in pressure in the chargedbeam irradiation chamber are further reduced by one more partition, thusmaking it possible to reduce variations in pressure to a level causingsubstantially no problem.(5) An increase in pressure when the stage is moved can be reduced to alow level.(6) An increase in pressure when the stage is moved can be reduced to alower level.(7) An inspection apparatus having a high performance in positioning ofthe stage and having a stabilized degree of vacuum of the charged beamirradiation area can be achieved, thus making it possible to provide aninspection apparatus having a high inspection performance and notcontaminating the sample.(8) A light-exposure apparatus having a high performance in positioningof the stage and having a stabilized degree of vacuum of the chargedbeam irradiation area can be achieved, thus making it possible toprovide a light-exposure apparatus having a high exposure accuracy andnot contaminating the sample.(9) A semiconductor is produced by an apparatus having a highperformance in positioning of the stage and having a stabilized degreeof vacuum of the charged beam irradiation area, whereby a finesemiconductor circuit can be formed.

Furthermore, it is apparent that the stage apparatus of FIGS. 138 to 144can be applied to the stage 13•6 of FIG. 13.

Another embodiment of the XY stage according to the present inventionwill be described with reference to FIGS. 145 to 147. Furthermore, inthe example of the conventional technique and embodiment of FIG. 148,like reference numerals are given to common components. Furthermore, the“vacuum” means a vacuum called in the art, and does not necessarilyrefer to an absolute vacuum.

Another embodiment of the XY stage is shown in FIG. 145. The leading endportion of a column 145•1 irradiating a charged beam to a sample, i.e. acharged beam irradiating portion 145•2 is attached to a housing 145•3sectioning a vacuum chamber C. The sample W placed on a table movable inthe X direction (lateral direction in FIG. 145) of an XY stage 145•4 isplaced just below the column. The charged beam can be applied accuratelyto any position on the surface of the sample W by the high-accurate XYstage 145•4.

A seat 145•5 of the XY stage 145•4 is fixed on the bottom wall of thehousing 145•3, and a Y table 145•6 moving in the Y direction (directionperpendicular to the plane in FIG. 145) is placed on the seat 145•5.Raised portions protruding into recessed grooves formed on a pair of Ydirection guides 145•7 and 145•8 placed on the seat 145•5 on the sidefacing the Y table are formed on both side faces (left and right sidefaces in FIG. 145) of the Y table 145•6. The recessed groove extends inthe Y direction over almost the entire length of the Y direction guide.Static-pressure bearings 145•9, 145•10, 145•11 and 145•12 each having awell known structure are provided on the upper and lower faces and theside faces, respectively, of the raised portion protruding into therecessed groove, and by blowing high-pressure gas via thesestatic-pressure bearings, the Y table 145•6 is supported on the Ydirection guides 145•7 and 145•8 in a non-contact manner, and cansmoothly reciprocate in the Y direction. Furthermore, a linear motor145•13 having a well known structure is placed between the seat 145•5and the Y table 145•6, and drive in the Y direction is performed by thelinear motor. High-pressure gas is supplied to the Y table through aflexible tube 145•14 for supply of high-pressure gas, and high-pressuregas is supplied to the static-pressure bearings 145•10 and 145•9 and145•12 and 145•11 through a gas channel (not shown) formed in the Ytable. The high-pressure gas supplied to the static-pressure bearings isejected into a gap of several microns to several tens of microns formedbetween opposite guide surfaces of the Y direction guide to correctlyposition the Y table in the X direction and Z direction (verticaldirection in FIG. 145) with respect to the guide surface of the Y table.

An X table 145•14 is placed or the Y table such that it is movable inthe X direction (lateral direction in FIG. 145). On the Y table 145•6, apair of X direction guides 145•15 (145•16) (only X direction guide145•15 is shown) having the same structure as those of the Y directionguides 145•7 and 145•8 for the Y table are provided with the X table145.14 held therebetween. A recessed groove is formed on the X directionguide on the side facing the X table, and a raised portion protrudinginto the recessed groove is formed on the side pert (side part facingthe X direction guide) of the X table. The recessed groove extends overalmost the entire length of the X direction guide. Static-pressurebearings (not shown) similar to the static-pressure bearings 145•9,145•10, 145•17, 145•11, 145•12 and 145•18 are provided in a similararrangement on the upper and lower faces and the side faces of the Xdirection table 145•14 protruding into the recessed groove. A linearmotor 145•19 having a well known structure is placed between the Y table145•6 and the X table 145•14, and the X table is driven in the Xdirection by the linear motor. High-pressure gas is supplied to the Xtable 145•14 through a flexible tube 145•20, and high-pressure gas issupplied to the static-pressure bearing. This high-pressure gas isejected from the static-pressure bearings to the guide surface of the Xdirection guide, whereby the X table 145•14 is accurately supported onthe Y direction guide in a non-contact manner.

The vacuum chamber C is evacuated through vacuum tubes 145•21, 145•22and 145•23 connected to a vacuum pump or the like having a well knownstructure. The tubes 145•22 and 145•23 on the inlet side (inner side ofvacuum chamber) extend through the seat 145•5, and form on the upperface thereof openings near the position at which the high-pressure gasis discharged from the XY stage 145•4, and prevent an increase inpressure within the vacuum chamber due to the high-pressure gas ejectedfrom the static-pressure bearings where possible.

A differential exhaust mechanism 145•24 is provided around the leadingend portion of the column 145•1. i.e. a charged beam irradiating portion145•2, so that the pressure of a charged beam irradiation space 145•25is kept at a sufficiently low level even if the pressure within thevacuum chamber C is high. That is, A cyclic member 145•26 of thedifferential exhaust mechanism 145•24 provided around the charged beamirradiating portion 145•2 is positioned with respect to the housing145•3 so that a very small gap (several microns to several hundreds ofmicrons) 145•27 is formed between the lower face (face on the sample Wside) of the cyclic member 145•26, and a cyclic groove 145•28 is formedon the lower face thereof. The cyclic groove 145•28 is connected to avacuum pump or the like (not shown) by an exhaust tube 145•29. Thus, thevery small gap 145•27 is evacuated through the cyclic groove 145•28 andthe exhaust port 145•29, and gas molecules about to enter the space145•25 surrounded by the cyclic member 145•26 from the vacuum chamber Cis discharged. In this way, the pressure within the charged beamirradiation space 145•25 can be kept at a low level, and the chargedbeam can be applied without any problems. This cyclic groove may have adouble or triple structure depending on the pressure within the chargedbeam irradiation space 145•25.

For the high-pressure gas supplied to the static-pressure bearing, drynitrogen is generally used. However, if possible, inert gas of higherpurity is preferably used. This is because if impurities such as waterand oil are contained in the gas, the impurity molecules are depositedon the inner surface of the housing sectioning the vacuum chamber andthe surfaces of stage components to reduce the degree of vacuum, anddeposited on the sample surface to reduce the degree of vacuum in thecharged beam irradiation space. Furthermore, in the above description,the sample W is not usually placed directly on the X table, but placedon a sample table having functions of detachably holding the sample,slightly changing the position with respect to the XY stage 145•4, andso on, but existence/nonexistence of the sample table and its structureare not related to the spirit of this embodiment, and are thereforeomitted for the sake of simplification.

In the charged beam apparatus described above, the stage mechanism ofthe static-pressure bearing that is used in the atmosphere can be almostdirectly used, thus making it possible to achieve a high-accuracy XYstage equivalent to the atmosphere high-accuracy stage for use in thelight-exposure apparatus or the like for the XY stage for charged beamapparatus at almost the same cost and in almost the same size.Furthermore, the structure and layout of the static-pressure guide andthe actuator (linear motor) described above are only one example, andany static-pressure guide and actuator capable of being used in theatmosphere may be employed.

Next, examples of values of sizes of the cyclic member 145•26 of thedifferential exhaust mechanism and the cyclic groove formed thereon areshown in FIG. 146. Furthermore, in this example, the cyclic groove has adouble structure of structures 146•1 and 146•2, and these structures areisolated from each other in the radial direction.

The flow rate of high-pressure gas supplied to the static-pressurebearing is usually about 20 L/min (atmospheric pressure equivalent).Provided that the vacuum chamber C is evacuated through a vacuum tubehaving an inner diameter of 50 mm and a length of 2 m by a dry pumphaving a pumping speed of 2000 L/min the pressure within the vacuumchamber is about 160 Pa (about 1.2 Torr). At this time, if the sizes ofthe cyclic member 146•3 of the differential exhaust mechanism, thecyclic groove and the like are set to those shown in FIG. 146, thepressure within the charged beam irradiation space 141•1 can be kept at10⁻⁴ Pa(10⁻⁶ Torr).

Another embodiment of the XY stage is shown in FIG. 147. A dry pump147•4 is connected through vacuum tubes 147•2 and 147•3 to the vacuumchamber C sectioned by a housing 147•1. Furthermore, a turbo-molecularpump 147•9 being an ultrahigh vacuum pump is connected to a cyclicgroove 147•6 of a differential exhaust mechanism 147•6 through a vacuumtube 147•8 connected to an exhaust port 147•7. Further, aturbo-molecular pump 147•13 is connected to the inside of a column147•10 through a vacuum tube 147•12 connected to an exhaust port 147•11.These turbo-molecular pumps 147•9 and 147•13 are connected to the dryvacuum pump 147•4 by vacuum tubes 147•14 and 147•15. In the figure, onedry vacuum pump is used for the roughing vacuum pump of theturbo-molecular pump and the pump for evacuation of the vacuum chamber,but they may be evacuated with dry vacuum pumps of different systemsdepending on the flow rate of high-pressure gas supplied to thestatic-pressure bearing of the XY stage, the volume and the area of theinner surface of the vacuum chamber, and the inner diameter and thelength of the vacuum tube.

High-purity inert gas (N₂ gas, Ar gas, etc.) is supplied to thestatic-pressure bearing of the XY stage through flexible tubes 147•16and 147•16. The gas molecules ejected from the static-pressure bearingdiffuse into the vacuum chamber, and are discharged by the dry vacuumpump 147•4 through exhaust ports 147•18, 147•19 and 147•20. Furthermore,these gas molecules entering the differential exhaust mechanism and thecharged beam irradiation space are suctioned through the cyclic groove147•6 or the leading end portion of the column 147•10, discharged by theturbo-molecular pumps 147•9 and 147•13 through the exhaust ports 147•7and 147•11, discharged from the turbo-molecular pumps, and thendischarged by the dry vacuum pump 147•4. In this way, the high-purityinert gas supplied to the static-pressure bearing is collected in thedry vacuum pump and discharged.

On the other hand, the exhaust port of the dry vacuum pump 147•4 isconnected to a compressor 147•22 through a tube 147•21, and the exhaustport of the compressor 147•22 is connected to the flexible tubes 147•16and 147•17 through tubes 147•23, 147•24 and 147•25 and regulators 147•26and 147•27. Accordingly, the high-purity inert gas discharged from thedry vacuum pump 147•4 is pressured again by the compressor 147•22,adjusted to have an appropriate pressure by the regulators 147•26 and147•27, and then supplied again to the static-pressure bearing of the XYstage.

Furthermore, since the gas supplied to the static-pressure bearingshould be purified as highly as possible, as described above, so that nowater and oil is contained in the gas, the turbo-molecular pump, the drypump and the compressor are required to have a structure such that nowater and oil enters the gas channel. Furthermore, it is also effectiveto a cold trap, filter or the like (147•28) is provided at some midpointin the tube 147•23 on the discharge side of the compressor to trapimpurities such as water and oil entering the circulating gas, so thatthey are not supplied to the static-pressure bearing.

Consequently, the high-purity inert gas can be circulated and reused,thus making it possible to save the high-purity inert gas, and the inertgas is not discharged into a room where this apparatus is installed,thus making it possible to eliminate the possibility that accidents suchas suffocation by inert gas occur.

A high-purity inert gas supply system 147•29 is connected to acirculation piping system, and plays a role to fill high-pressure inertgas in the entire circulation system including the vacuum chamber C, thevacuum tubes 147•8, 147•12, 147•14, 147•15, 147•2 and 147•3 and thepressure tubes 147•21, 147•23, 147•24, 147•25 and 147•30 whencirculation of the gas is started, and a role to supply an amount of gasequivalent to a shortfall in case where the flow rate of gas drops forsome cause. Furthermore, by imparting to the dry vacuum pump 147•4 afunction of compression to an atmospheric pressure or higher, one pumpcan be made to serve as both the dry vacuum pump 147•4 and compressor147•22.

Further, for the ultrahigh vacuum pump for use in evacuation of thecolumn, a pump such as an ion pump or getter pump may be used instead ofthe turbo-molecular pump. However, if such an entrapment vacuum pump isused, the circulation piping system cannot be built in the area of thepump. Furthermore, instead of the dry vacuum pump, a dry pump of adifferent system such as diaphragm-type dry pump may be used as a matterof course.

An optical system and a detector of the charged beam apparatus accordingto this embodiment are schematically shown in FIG. 149. The opticalsystem is provided in a column, but the optical system and detector areillustrative, and any optical system and detector may be used asrequired. An optical system 149•1 of the charged beam apparatuscomprises a primary optical system 149•3 irradiating a charged beam to asample W placed on a stage 149•2, and a secondary optical system 149•4into which secondary electrons emitted from the sample are introduced.The primary optical system 149•3 comprises an electron gun 149•5emitting a charged beam, a lens system 149•6 constituted by two-stageelectrostatic lens converging the charged beam emitted from the electrongun 149•5, a deflector 149•7, a Wien filter or E×B separator 149•8deflecting the charged beam so that its optical axis is perpendicular tothe surface of the object, and a lens system 149•9 constituted by atwo-stage lens, and these components are placed in order slantingly withrespect to the line of the optical axis of the charged beamperpendicular to the surface of the sample (sample surface) with theelectron gun 149•5 situated at the uppermost position as shown in FIG.149. The E×B deflector 149•8 comprises an electrode 149•10 and a magnet149•11.

The secondary optical system 149•4 is an optical system into whichsecondary electrons emitted from the sample W are introduced, andcomprises a lens system 149•12 constituted by a two-stage electrostaticlens placed on the upper side of the E×B deflector 149•8 of the primaryoptical system. A detector 149•13 detects secondary electrons sentthrough the secondary optical system 149•4. The structures and functionsof the components of the optical system 149•1 and the detector 149•13are the same as those of the conventional system, and therefore detaileddescriptions thereof are not presented.

The charged beam emitted from the electron gun 149•5 is shaped by asquare aperture of the electron gun, downscaled by the two-stage lenssystem 149•6, and has the optical axis adjusted by the deflector 149•7to form an image of a square of 1.925 mm×1.925 mm on the deflectioncentral plane of the E×B deflector. The E×B deflector 149•8 has astructure such that an electric field is orthogonal to a magnetic fieldin the plane perpendicular to the normal line of the sample, in whichwhen a relation in energy between the electric field and the magneticfield and the electron meets a certain requirement, the electron is madeto travel in a straight line, and otherwise deflected in a predetermineddirection according to the mutual relation between the electric fieldand the magnetic field and the electric field. In FIG. 149, the chargedbeam from the electron gun is made to enter the sample W at a rightangle, and secondary electrons emitted from the sample are made totravel toward the detector 149•13 in a straight line. The shaped beamdeflected by the E×B deflector is downscaled to ⅕ of the original scaleby the lens system 149•9 and projected on the sample W. Secondaryelectrons having information of a pattern image, emitted from the sampleW, are enlarged by the lens systems 149•9 and 149•4 and form a secondaryelectron image in the detector 149•13. This four-stage enlargement lensis a deformation-free lens because the lens system 149•9 forms asymmetric tablet lens and the lens system 149•12 also forms a symmetrictablet lens.

According to this embodiment, the following effects can be exhibited.

(1) Using a stage having a structure similar to that of astatic-pressure bearing-type stage that is generally used in theatmosphere (static-pressure bearing support-type stage having nodifferential exhaust mechanism), a sample on the stage can be stablyprocessed with a charged beam.(2) Influences on the degree of vacuum of a charged beam irradiationarea can be reduced to a minimum, and processing of the sample with thecharged beam can be stabilized.(3) An inspection apparatus having a high performance in positioning ofthe stage and having a stabilized degree of vacuum of the charged beamirradiation area can be provided at a low cost.(4) A light-exposure apparatus having a high performance in positioningof the stage and having a stabilized degree of vacuum of the chargedbeam irradiation area can be provided at a low cost.(5) A semiconductor is produced by an apparatus having a highperformance in positioning of the stage and having a stabilized degreeof vacuum of the charged beam irradiation area, whereby a finesemiconductor circuit can be formed.

3-2) Other Embodiments of Electron Beam Apparatus

Further, another system with consideration of solving the problems ofthis projection electron microscope type system is a system in whichusing a plurality of primary electron beams, the plurality of electronbeams are scanned two-dimensionally (in X-Y direction) (raster-scanned)to irradiate observation areas of the sample surface, and the secondaryelectro-optical system employs a projection system.

This system has the advantage of the projection type system describedpreviously, and can solve the problems of this mapping system such that(1) charge-up easily occurs on the sample surface because the electronbeam is collectively applied, and (2) the current of the electron beamobtained with this system is limited (to about 1.6 μA), which hinders animprovement in inspection speed, by scanning a plurality of electronbeams. That is, because the electron beam irradiation spot is shifted,the charge easily escapes, resulting in a reduction in charge-up.Furthermore, by increasing the number of the electron beams, the currentvalue can easily be increased. In the embodiment, if four electron beamsare used, total 2 μA of current is obtained with 500 nA of current forone electron beam (diameter of electron beam: 10 μm). The number ofelectron beams can easily be increased to about 16 and in this case, itis possible to obtain 8 μA in principle. The scan of a plurality ofelectron beams is not limited to the raster scan described above, butmay be any other from of scan such as a Lissajou's figure as long as theamount of irradiation with a plurality of electron beams is uniformlydistributed over the irradiation area. Thus, the direction in which thestage is scanned is not necessarily be perpendicular to the direction ofscan of the electron beam.

3-2-1) Electron Gun (Electron Beam Source)

A thermal electron beam source is used as an election beam source foruse in this embodiment. The electron emission (emitter) material isLaB6. Any other material can be used as long as it is a material havinga high melting point (low vapor pressure at high temperature) and havinga small work function. To obtain a plurality of electron beams, twomethods are used. One is a method in which one electron beam is drawnfrom one emitter (one protrusion) and made to pass through a thin platehaving a plurality of holes (aperture plate) to obtain a plurality ofelectron beams, and the other is a method in which a plurality ofprotrusions are formed on one emitter and a plurality of electron beamsare draw directly therefrom. Both the methods utilize the nature suchthat the electron beam is easily emitted from the leading end of theprotrusion. Other types of electron beam sources, for example, a thermalelectron beam emission-type electron beam and a Shottky type can beused. Further, the electron beam gun may emit a rectangular or linearbeam, an aperture shape may be used to create such a shape, the electrongeneration portion (chip, filament or the like) of the electron gun maybe formed into a rectangular or linear shape.

Furthermore, the thermal electron beam source is a type of electron beamsource in which the electron emission material is heated to emitelectrons, and the thermal electric field emission electron beam sourceis a type of electron beam source in which a high electric field isapplied to the electron emission material to emit electrons, and theelectron beam emission portion is heated to stabilize the emission ofelectrons.

FIG. 150 A is a schematic diagram of electron beam apparatus of anotherembodiment. On the other hand, FIG. 150 B is a schematic diagram showingan aspect in which a sample is scanned with a plurality of primaryelectron beams. An electron gun 150•1 capable of being activated underspace-charge limitation conditions forms a multi-beam denoted byreference numeral 150•2 in FIG. 150 B. The multi-beam 150•2 isconstituted by primary electron beams 150•3 that are 8 circular beamssituated along a circumference.

A plurality of primary electron beams 150•3 generated at the electrongun 150•1 are converged using lenses 150•5 and 150•6, and is adapted toenter a sample W at a right angle by an E×B separator 150•9 comprised ofan electrode 150•7 and a magnet 150•8. The multi-beam 150•2 constitutedby a plurality of primary electron beams 150•3 converged on the sample Wby a primary optical system including the components 150•4, 150•5,150•6, 150•9, a lens 150•10 and an objective lens 150•11 is used forscanning on the sample W by a two-stage deflector (not shown, includedin the primary optical system) provided on the downstream side of thelens 150•6.

The sample W is scanned in the direction of the x axis with the mainface of the objective lens 150•11 as the center of reflection. As shownin FIG. 150 B, the primary electron beams 150•3 of the multi-beam 150•2are situated at a distance from each other along a circumference, andare designed so that the distances between the mutually adjacent primaryelectron beams 150•3 (measured at the center of each primary electronbeam) are the same when the primary electron beams 150•3 are projectedon the y axis orthogonal to the x direction being a scan direction. Atthis time, the mutually adjacent primary electron beams 150•3 may beseparated from each other, contact each other or partially overlap eachother.

The overlapping pitch may be set to any value equal to or smaller than100 μm, preferably equal to or smaller than 50 μm, more preferably equalto or smaller than 10 μm. By setting the overlapping pitch to a valueequal to or smaller than the pitch of the beam shape, beams can be madeto contact one another to form a linear shape. Furthermore, beamsoriginally formed into a rectangular or linear shape may be used.

As shown in FIG. 150 B, the primary electron beams 150•3 constitutingthe multi-beam 150•2 are situated at a distance from one another,whereby the limit value of the current density of the individual primaryelectron beam, i.e. the marginal current density value causing no chargeon the sample W can be maintained at a level equivalent to that when asingle circular beam is used, thereby making it possible to prevent adrop in S/N ratio. Furthermore, the primary electron beams 150•3 aresituated at a distance from one another, and thus the space chargeeffect is insignificant.

On the other hand, the multi-beam 150•2 can scan the sample W over anentire filed of view 150•12 in a uniform density with one scan.Consequently, image formation can be performed in high throughput, thusmaking it possible to achieve a reduction in inspection time. In FIG.150 B, provided that reference numeral 150•2 denotes a multi beam at thestarting point of scanning, reference numeral 150•13 denotes amulti-beam at the endpoint of scanning.

The sample W is placed on a sample table (not shown). This table iscontinuously moved along the y direction orthogonal to the scandirection x at the time when the sample W is scanned in the x direction(e.g. scanned in a width of 20 μm). In this way, raster scanning isperformed. A drive apparatus (not shown) for moving the table having thesample placed thereon.

Secondary electrons generated from the sample W during scanning andemitted in various directions are accelerated in the direction of theoptical axis by the objective lens 150•11 and as a result, the secondaryelectrons emitted in various directions from various points are eachnarrowly converged, and intervals of images are enlarged with lenses150•10, 150•11, 150•14 and 150•15. A secondary electron beam 150•16formed via a secondary optical system including the lenses 150•10,150•11, 150•14 and 150•15 is projected on the light-receiving surface ofa detector 150•17 to form an enlarged image of a field of view.

The detector 150•17 included in the optical system amplifies thesecondary electron beam with an MCP (micro-channel plate), converts theamplified secondary electron beam into an optical signal with ascintillator, and converts the optical signal into an electric signalwith a CCD detector. By the electric signal from the CCD, atwo-dimensional image of the sample W can be formed. Each primaryelectron beam 150•3 should have a dimension of at least two pixels ofCCD pixels.

By operating the electron gun 150•1 under space-charge limitationconditions, the shot noise of the primary electron beam 150•3 can bereduced in a order of one digit compared to operating the electron gununder temperature limitation conditions. Thus, the shot noise of thesecondary electron signal can be reduced in a order of one digit, thusmaking it possible to obtain a signal of a high S/N ratio.

According to the electron beam apparatus of this embodiment, the limitvalue of the current density of the primary electron beam causing nocharge on the sample is maintained at a level equivalent to that when asingle circular beam is used, whereby a drop in S/N ratio is prevented,and images are formed in high throughput, whereby inspection time can bereduced.

In the device production process according to this embodiment, such anelectron beam apparatus is used to evaluate the wafer after each waferprocess is completed, whereby an improvement in yield can be achieved.

FIG. 151 shows the details of the electron beam apparatus according tothe embodiment of FIG. 150 A. Four electron beams 151•2 (151•3 to 151•6)emitted from an electron gun 151•1 are shaped by an aperture diaphragm151•7, made to form an elliptic image of 10 μm×12 μm at the central faceof deflection of a Wien filter 151•10 by two-stage lenses 151•8 and151•9, raster-scanned by a deflector 151•11, and made to form an imageso as to uniformly cover a rectangular area of 1 mm×0.25 mm as entirefour electron beams. A plurality of electron beams deflected by the E×B151•10 form a crossover with an NA diaphragm, and are downscaled to ⅕ ofthe original scale by the lens 151•11 to cover the sample with an areaof 200μ×50 μm, and applied and projected on the sample surface at aright angle (called Koehler illumination). Four secondary electron beams151•12 having information of an pattern image (sample image F), emittedfrom the sample, are enlarged by lenses 15•11, 151•13, 151•14, and forman image on an MCP 151•15 as a rectangular image (enlarged projectionimage F) synthesized with the four secondary electron beams as a whole.The enlarged projection image F with the four secondary electron beams151•12 are intensified by a factor of ten thousands by the MCP 151•15,converted into light by a fluorescent screen, changed to an electricsignal synchronized with the speed of continuous movement of the sampleat a TDI-CCD 151•16, acquired as a continuous image at an image displayunit 151•17, and outputted to a CRT or the like.

The electron beam irradiating portion should irradiate the samplesurface with an electron beam in an elliptic or rectangular form asuniformly as possible and with reduced irradiation unevenness, andshould irradiate the irradiation area with the electron beam with alarger current to improve the throughput. In the conventional system,the electron beam irradiation unevenness is about ±10%, the image haslarge contrast unevenness, and the electron beam irradiation current isonly about 500 nA in the irradiation area, resulting in a problem suchthat high throughput cannot be obtained. Furthermore, this system has aproblem such that image formation tends to be hindered due to charge-upbecause a wide image observation area is correctively irradiated withthe electron beam, compared with the scanning electron beam microscope(SEM) system.

A method for irradiating a primary electron beam in this embodiment isshown in FIG. 152. A primary electron beam 152•1 is constituted by fourelectron beams 152•2 to 152•5, each beam has an elliptic shape of 2μm×2.4 μm, a rectangular area of 200 μm×12.5 μm is raster-scanned withone beam, and the beams are added together in such a manner that they donot overlap one another to irradiate a rectangular area of 200μ×50 μm asa whole. The beam 151•2 reaches a spot 151•2′ in finite time, thenreturns to just below the spot 151•2 shifted by the diameter of the beamspot (10 μm) with almost no time loss, moves again to just below thespot 151•2′ (toward a spot 151•3′) in parallel to the line 151•2 to151•2′ in finite time in the same manner as described previously,repeats this scan to scan ¼ of a rectangular irradiation area (200μm×12.5 μm) shown by the dotted line in the figure, then returns to theoriginal spot 152•1, and repeats this scan at a high speed.

The other electron beams 152•3 to 152•5 repeat scans at the same speedas in the case of the electron beam 152•2 to scan the rectangularirradiation area (200μ×50 μm) as a whole uniformly and at a high speed.

The scan is not limited to the raster scan as long as the sample can beuniformly irradiated. For example, the sample may be scanned in such amanner as to draw a Lissajou's figure. Thus, the direction of movementof the stage is not limited to the direction A shown in the figure. Inother words, the direction is not necessarily perpendicular to the scandirection (lateral high-speed scan direction in the figure).

In this embodiment, the sample can be irradiated with electron beamirradiation unevenness of about ±3%. The irradiation current is 250 nAfor one electron beam, and 1.0 μA of irradiation current can be obtainedwith four electron beams as a whole on the sample surface (twice aslarge as the irradiation current in the conventional system). Byincreasing the number of electron beams, the current can be increased,and thus high throughput can be obtained. Furthermore, the irradiationspot is small compared to the conventional system (about 1/80 in area),and the charge-up can be reduced to 1/20 of that of the conventionalsystem because the sample is moved.

Although not shown in the figure, this apparatus comprises unitsrequired for irradiation with the electron beam and image formation suchas a limitation field diaphragm, a deflector (aligner) having 4 or morepoles for adjustment of the axis of the electron beam, an astigmatismcorrector (stigmater), and a plurality of quadrupolar lenses (quadrupolelenses) for shaping a beam, in addition to lenses.

3-2-2) Structure of Electrode

FIG. 153 shows an electron beam apparatus having an electrode structurefor preventing insulation breakdown in an electro-optical system usingan electrostatic lens for irradiating the sample with an electron beam.

Considerations have been made for using an electron beam apparatus ofhigh sensitivity and high resolution using an electron beam to inspectthe surface state of a fine sample such that a sufficient sensitivityand resolution cannot be obtained by optical inspection.

In this electron beam apparatus, an electron beam is emitted by anelectron beam source, the emitted electron beam is accelerated andconverged with an electrostatic system such as an electrostatic lens,and made to enter a sample as an inspection object. Then, a secondaryelectron beam emitted from the sample with entrance of the electron beamis detected, whereby a signal matching the detected secondary electronbeam is generated, and for example, data of the sample is formed withthis signal. The formed data is used to inspect the surface state of thesample.

In the electro-optical system using an electrostatic lens such as anelectrostatic lens for use in the electron beam apparatus, electrodesgenerating electric fields for accelerating and converging the electronbeam are provided in multiple stages along the optical axis of theelectron beam. A predetermined voltage is applied to each of theseelectrodes and in this way, the electron beam is accelerated andconverged to a predetermined spot on the optical axis by the electricfield produced due to a difference in potential between electrodes.

In the conventional electron beam apparatus, part of the electron beamemitted from the electron beam source may impinge upon the electrodeirrespective of the electric field in the electro-optical system usingthe electrostatic lens. In this case, as the electron beam impinges uponthe electrode, a secondary electron beam is emitted from the electrodeitself. The amount of the secondary electron beam emitted from theelectrode varies depending on the material of the electrode, or thematerial coated on the electrode. If the amount of the secondaryelectron beam emitted from the electrode increases, the secondaryelectron beam is accelerated by the electric field of the electrode andionizes residual gas in the apparatus, and the ions impinge upon theelectrode, whereby a secondary electron beam is further emitted from theelectrode. Therefore, if a large amount of secondary electron beam isemitted, a discharge tends to occur between electrodes, thus raising theprobability of occurrence of insulation breakdown between electrodes.

For example, comparison of the probability of insulation breakdownbetween the electrode coated with aluminum and the electrode coated withgold showed that the probability of insulation breakdown betweenelectrodes was slightly higher in the case of the electrode coated withaluminum. The work function of aluminum is 4.2 [eV] and the workfunction of gold is 4.9 [eV]. Here, the work function means minimumenergy required for taking one electron beam in a metal into a vacuum(unit: eV).

Furthermore, if the electrode is coated with gold, and the sample in theelectron beam apparatus is a semiconductor wafer, the gold may bespattered and deposited on the surface of the semiconductor wafer as theelectron beam impinges upon the gold coating. If the gold is depositedon the surface of the semiconductor, the gold is scattered in siliconcrystals in a subsequent heating step, resulting in degradation inperformance of a transistor. Thus, in this case, the electron beamapparatus is not suitable for inspection of semiconductor wafers.

On the other hand, for example, in the electrostatic lens of theelectro-optical system using an electrostatic lens, an electrostaticlens having a small focal distance is obtained by reducing the distancebetween electrodes. If the focal distance is small, the electrostaticlens has a reduced aberration coefficient and hence a low aberration,and therefore the resolution of the electrostatic lens increases,resulting in an improvement in resolution of an evaluation apparatus.

Also, by increasing a difference in potential to given to betweenelectrodes of the electrostatic lens, the focal distance of theelectrostatic lens can be reduced. Accordingly, as in the case ofreducing the distance between electrodes, the electrostatic lens has alow aberration and a high resolution, and thus the resolution of theelectron beam apparatus is improved. Thus, if the distance betweenelectrodes is reduced and the difference in potential between electrodesis increased, a reduction in aberration and an increase in resolution ofthe electrostatic lens can be achieved in a synergistic manner. However,if the distance between electrodes is reduced and the difference inpotential between electrodes is increased, a discharge tends to occurbetween electrodes, thus increasing the probability of occurrence ofinsulation breakdown between electrodes.

Hitherto, the insulation between electrodes has been retained byinserting an insulating material between electrodes, and supporting theelectrodes with this insulating material. Furthermore, the insulationperformance of the insulating material has been improved by increasingthe shortest creepage distance (insulation surface length) of theinsulating material between electrodes. For example, by forming thesurface of the insulating material into a corrugation along the distancebetween electrodes, the shortest creepage distance between electrodescan has been increased.

Generally, however, the processing of the surface of the insulatingmaterial is difficult compared to the processing of a metal, and thusrequires a high process cost. Furthermore, if the surface of theinsulating material is formed into a corrugation, the surface area ofthe insulating material is increased, and therefore the amount of gasemitted from the insulating material may increase in the case where avacuum is maintained in the electron beam apparatus. Accordingly, therehave been many cases where the degree of vacuum decreases, resulting ina drop in withstand pressure between electrodes.

The embodiment of FIG. 153 has been proposed for solving these problems,and the configuration and operation of a projection electron microscopetype evaluation apparatus and a device production process using theapparatus where an electron beam apparatus capable of preventinginsulation breakdown between electrodes of an electrostatic opticalsystem is applied to the projection electron microscope type evaluationapparatus having the electrostatic optical system, according to thisembodiment, will be described below.

In FIG. 153, for a projection electron microscope type evaluationapparatus 153•1, an electron beam applied to a sample has predeterminedemitting surface, and a secondary electron beam emitted from the samplewith irradiation of the electron beam also has a predetermined emittingsurface. An electron beam having a two-dimensional area, for examplerectangular emitting surface is emitted from an electron beam source153•2, and enlarged by a predetermined magnification by an electrostaticlens system 153•3. The enlarged electron beam is made to enter an E×Bdeflector 153•4 slantingly from above, and deflected toward asemiconductor wafer 153•5 as a sample (solid line in FIG. 153) by afield in which an electric field and a magnetic field of the E×Bdeflector 153•4 are orthogonal to each other.

The electron beam deflected toward the semiconductor wafer 153•5 by theE×B deflector 153•4 is retarded by an electric field produced by avoltage applied to electrodes in an electrostatic objective lens system153•6, and made to form an image on the semiconductor wafer 153•5 by theelectrostatic objective lens system 153•6.

Then, the secondary electron beam produced with irradiation of theelectron beam to the semiconductor wafer 153•5 is accelerated toward adetector 153•7 (dotted line in FIG. 153) by the electric field of theelectrostatic objective lens system 153•6, and made to enter the E×Bdeflector 153•4. The E×B deflector 153•4 forces the acceleratedsecondary electron beam toward an electrostatic intermediate lens system153•8, then causes the electrostatic intermediate lens system 153•8 tomake the secondary electron beam enter the detector 153•7, whereby thesecondary electron beam is detected. The secondary electron beamdetected by the detector 153•7 is converted into data and sent to adisplay apparatus 153•9, an image of the electron beam is displayed onthe display apparatus 153•9, and a pattern of the semiconductor wafer153•5 is inspected.

The configurations of the electrostatic lens system 153•3, theelectrostatic objective lens system 153•6, the electrostaticintermediate lens system 153•8 and the E×B deflector 153•4 in theprojection type evaluation apparatus 153•1 will now be described indetail. The electrostatic lens system 153•3 and the electrostaticobjective lens system 153•6 through which the electron beam passes, andthe electrostatic intermediate lens system 153•8 through which thesecondary electron beam passes include a plurality of electrodes forproducing a predetermined electric field. Furthermore, the surfaces ofall the electrodes are coated with platinum. Further, the surface of anelectrode 153•10 of the E×B deflector 153•4 is also coated withplatinum.

Now, the probability of occurrence of insulation breakdown for eachmetal coated on the electrode will be described with reference to FIG.154. Furthermore, in the projection type evaluation apparatus, otherinspection conditions excluding the type of metal coated on theelectrode are the same.

First, comparison in probability of occurrence of insulation breakdownbetween the case where aluminum is used as a metal coated on theelectrode and the case where gold is used as such a metal showed thatthe probability of occurrence of insulation breakdown was slightly lowerin the electrode coated with gold. Thus, it was shown that gold had moreeffective in prevention of insulation breakdown. Furthermore, comparisonin probability of occurrence of insulation breakdown between the casewhere gold is used as a metal coated on the electrode and the case whereplatinum is used as such a metal showed that the probability ofoccurrence of insulation breakdown was lower in the electrode coatedwith platinum.

Here, the work functions of the metals are 4.2 [eV] for aluminum, 4.9[eV] for gold, and 5.3 [eV] for platinum. The work function of the metalmeans minimum energy (unit: eV) required for taking one electron in themetal into a vacuum. That is, as the value of the work functionincreases, the electron beam becomes harder to be taken.

Accordingly, in the projection type evaluation apparatus 153•1, when theelectron beam emitted from the electron beam source 153•2 impinges uponthe electrode, the amount of secondary electron beam emitted from theelectrode decreases and thus the probability of occurrence of insulationbreakdown of the electrode is reduced as long as the electrode is coatedwith a metal having a large work function value (including an alloyhaving as a main material a metal having a large work function value).Therefore, any material having a large work function is somewhatacceptable. Specifically, if the work function of the metal coated onthe electrode is 5 [eV], the probability of occurrence of insulationbreakdown of the electrode can be kept at a low level.

Furthermore, if, as in this embodiment, the sample to be inspected isthe semiconductor wafer 153•5, and the metal coated on the electrode isgold, gold may be deposited on the pattern of the semiconductor wafer153•5 as the electron beam impinges upon the gold. Accordingly, in thisembodiment, if the metal coated on the electrode is platinum, platinumis never deposited on the pattern of the semiconductor wafer 153•5, andthe device performance is never compromised even if the platinum isdeposited on the pattern. Further, the probability of occurrence ofinsulation breakdown of the electrode can be reduced, and thus platinumis more preferable.

One example of the shape and configuration of the electrode will now bedescribed with reference to FIGS. 155 and 156. In FIG. 155, an electrode155•1 is an electrode of an electrostatic lens included in theelectrostatic lens system 153•3, the electrostatic objective lens system153•6 and the electrostatic intermediate lens system 153•8.

The electrode 155•1 has a disk-like shape having at almost the center athrough-hole allowing the electron beam and secondary electron beam topass therethrough, and in the projection type evaluation apparatus 153•1of this embodiment, a predetermined voltage is applied to the electrode155•1 by a power supply apparatus (not shown).

FIG. 156 is a partial sectional view of a surface portion of theelectrode 155•1. Furthermore, the surface of the electrode 153•10 of theE×B deflector 153•4 may have the same configuration as that of thesurface of the electrode 155•1. The electrode 155•1 is made of siliconcopper (silicon bronze) 156•1, and titanium 156•2 is sputter-coated inthe thickness of 50 nm on the silicon copper 156•1 processed into anecessary size and shape, and platinum 156•3 is sputter-coated in thethickness of 200 nm on the titanium 156•2 to form the electrode 155•1.

Now, the electron configuration for preventing insulation breakdownbetween electrodes when the difference in potential between electrodesis large in this embodiment will now be described in detail withreference of FIGS. 157 and 158. Electrodes 157•1 and 157•2 of FIG. 157are, for example, electrodes included in the electrostatic objectivelens system 153•6, and the electrodes are coated with platinum asdescribed above. Furthermore, predetermined voltages are applied to theelectrodes 157•1 and 157•2 by a power supply apparatus (not shown). Inthis embodiment, a high voltage, for example a voltage of 15 kV isapplied to the electrode 157•2 on the semiconductor wafer 153•5 side,and a voltage of 5 kV is applied to the electrode 157•1.

A through-hole 157•3 through which the electron beam and the secondaryelectron beam pass is situated in the middle between the electrodes157•1 and 157•2, an electric field is formed in the through-hole 157•3by a difference in potential between the electrodes 157•1 and 157•2. Bythis electric filed, the electron beam is retarded and retarded, and isapplied to the semiconductor wafer 153•5. At this time the difference inpotential between the electrodes is large, and therefore theelectrostatic objective lens system 153•6 can have an electrostaticobjective lens having a small focal distance. Accordingly, theelectrostatic objective lens system 153•6 has a low aberration and ahigh resolution.

An insulating spacer 157•4 is inserted between the electrodes 157•1 and157•2, and the insulating spacer 157•4 approximately perpendicularlysupports the electrodes 157•1 and 157•2. The shortest creepage distancebetween electrodes in the insulating spacer 157•4 is proximately thesame as the distance between electrodes in the area of the supportedelectrode. That is, the surface of the insulating spacer 157•4 betweenelectrodes are not corrugated or the like, but is almost a straightline.

The electrode 157•2 has a first electrode surface 157•5 with theshortest distance between electrodes, a second electrode surface 157•6having a distance between electrodes longer than the first electrodesurface 157•5, and a step 157•7 in the direction of the distance betweenthese two electrodes between the first electrode surface 157•5 and thesecond electrode surface 157•6 (FIG. 158). The insulating spacer 157•4supports the electrode 157•2 with the second electrode surface 157•6.

Owing to this configuration of the electrode 157•2, the shortestcreepage distance of the insulating spacer 157•4 can be made to belonger than the shortest distance between electrodes with the shortestdistance between electrodes being kept at a predetermined distance andwithout processing the surface of the insulating spacer 157•4 into acorrugated shape in the direction of the distance between electrodes.Furthermore, since a large electric field is not applied to the surfaceof the insulating spacer 157•4, a structure can be provided such that acreepage discharge is hard to occur.

Thus, the electrostatic objective lens system 135•6 can be made to havean electrostatic objective lens having a small focal distance, and havea low aberration and a high resolution, and the performance of theinsulating spacer 157•4 to provide insulation between electrodes is notdegraded, thus making it possible to prevent insulation breakdownbetween electrodes. Furthermore, since the electrode 157•2 made of metalis processed so as to provide the step 157•7 thereon, the process costis reduced compared with the case where the insulating spacer 157•4 isprocessed. In addition, the surface of the insulating spacer 157•4 inthe direction of the distance between electrodes has almost noirregularities, and the amount of emitted gas from the insulating spacer157•4 never increases. Further, corner portions of an open end portion157•8 of the through-hole 157•3 of the electrode 157•1 and an open endportion 157•9 of the through-hole 157•3 of the electrode 157•2 havecurvatures, and therefore the electric field is never concentrated onboth the corner portions, thus making it possible to more reliablyprevent insulation breakdown between electrodes. Furthermore, a cornerportion of the step 157•7 of the electrode 157•2 on the side betweenelectrodes has a curvature, and therefore the electric field is neverconcentrated on the corner portion, thus making it possible to morereliably prevent insulation breakdown between electrodes.

Furthermore, in this embodiment, the step 157•7 is provided on theelectrode 157•2, but the electrode 157•1 may also be processed so as toprovide a step in the direction of the electrode 157•2, or only theelectrode 157•1 may be processed so as to provide a step in thedirection of the electrode 157•2 with the electrode 157•2 having nostep. Furthermore, the electrodes with the insulating spacer 157•4inserted therebetween has been described in the electrostatic objectivelens system 153•6, but if there are electrodes having a large differencein potential in other electrostatic lens system, the spacer 157•4 may beapplied to the electrostatic lens system to prevent insulation breakdownbetween electrodes.

By using the embodiment described with FIGS. 153 to 158 in inspectionsteps in the device production process already described, thesemiconductor wafer can be evaluated without causing insulationbreakdown to occur between electrodes of the electrostatic lens system.

3-3) Embodiment for Anti-Vibration Apparatus

This embodiment relates to an electron beam apparatus performing atleast any one of processing, production, observation and inspection of amaterial by irradiating an electron beam to the target position of thematerial, more particularly to an electron beam apparatus having reducedundesired mechanical vibrations occurring in a mechanical structurepositioning the electron beam, an anti-vibration method thereof, and asemiconductor production process comprising a step of performing atleast any one of processing, production, observation and inspection of asemiconductor device using the electron beam apparatus.

Generally, means for observing a fine structure of a material using anelectron beam includes an inspection apparatus for inspecting defects ofa pattern formed on a wafer or the like, a scanning electron beammicroscope (SEM) and the like but in this case, the observationresolution is μm to several tens of nm, and it is therefore required tosufficiently remove external vibrations to make an observation.Furthermore, in an apparatus for performing exposure system using anelectron beam, a vibration removal apparatus for sufficiently removingexternal vibrations should be used to deflect an electron beam tocorrectly irradiate the beam to the target position, and the rigidityshould be improved to reduce a drift caused by a mechanical resonanceresulting from the structure of a column portion to a minimum possiblelevel. To improve the rigidity of the structure, an improvement inrigidity by reduction in size can hardly achieved because of thephysical limitation in size due to the electro-optical system, and thusan improvement in rigidity is often achieved by thickening the wall ofthe column portion, increasing the size and so on. However, theimprovement in rigidity by this method has many disadvantages includingdesign restrictions on the degree of freedom including an increase inweight of apparatus, limitations on the shape and increase in size of avibration removal table, as well as economic aspects.

In view of the facts described above, this embodiment provides anelectron beam apparatus in which alleviation of design restrictions,reduction in size and weight of apparatus, and improvement in economyare achieved by appropriately attenuating undesired vibrations by aresonance of a mechanical structure for positioning a beam so that thepositioning of the beam can be maintained with high accuracy withoutnecessarily improving the rigidity of the mechanical structure, and asemiconductor production process capable of performing production,inspection, processing, observation and the like using the apparatus insteps of producing a semiconductor device.

FIG. 159 shows the configuration where this embodiment is applied to anelectron beam inspection apparatus inspecting defects of a semiconductorwafer using en electron beam. An electron beam inspection apparatus159•1 shown in this figure is so called a projection type apparatus, andhas a mechanical structure of an A block and a B block protruding upwardslantingly from the A block. Primary electron beam irradiating means forirradiating a primary electron beam is placed in the B block, and aprojection type optical system for mapping and projecting a secondaryelectron beam, and imaging means for detecting the intensity of thesecondary electron beam are included in the A block. The A block iscoupled to a lowermost fixation base 159•2.

The primary electron beam irradiating means placed in the B blockcomprises an electron beam source 159•3 constituted by a cathode and ananode to emit and accelerate a primary electron beam, an oblong opening159•4 shaping the primary electron beam into an oblong, and a quadrupolelens 159•5 reducing the primary electron beam and making the primaryelectron beam form an image in a reduced size. An E×B deflector 159•7deflecting the reduced primary electron beam so as to impinge upon asemiconductor wafer 159•6 at approximately a right angle in a field inwhich an electric field E and a magnetic filed B are orthogonal to eachother, an aperture (NA) 159•8, and an objective lens 159•9 making theprimary electron beam passing through the aperture form an image on thewafer 159•6 are placed in the lower part of the A block.

Here, the primary electron beam reduced by the quadrupole lens 159•5forms an image of, for example, 500 μm×250 μm on the deflection mainsurface of the E×B deflector 159•7, and also forms a crossover image ofthe electron beam source 159•3 on the aperture 159•8, so that Kellerillumination conditions are satisfied. An image of, for example, 100μm×50 μm is formed on the wafer 159•6 by the objective lens 159•6.

The wafer 159•6 is placed in a sample chamber (not shown) capable ofbeing evacuated, and also placed on a stage 159•10 movable in the X-Yhorizontal plane. Here, a relation between the A and B blocks and an XYZorthogonal coordinate system is shown in FIG. 160( a). The wafer surfaceis situated in the X-Y horizontal plane, and the Z axis is appropriatelyparallel to the optical axis of a projection optical system. As thestage 159•10 moves in the X-Y horizontal plane with the wafer 159•6placed thereon, the inspection surface of the wafer 159•6 issequentially scanned with the primary electron beam. Furthermore, thestage 159•10 is placed on the fixation base 159•2.

The projection type optical system placed in the upper part of the Ablock comprises an intermediate electrostatic lens 159•11, a projectionelectrostatic lens 159•12, and a diaphragm 159•13 placed in the middlebetween these lenses. A secondary electron beam, a reflection electronbeam and a scattered electron beam emitted from the wafer 159•6 withirradiation of the primary electron beam are projected under apredetermined magnification (e.g. by factor of 200 to 300), and made toform an image on the lower face of a micro-channel plate 159•14.

Imaging means placed at the top of the A block comprises themicro-channel plate 159•14, a fluorescent screen 159•15, a relay lens159•16 and an imaging unit 159•17. The micro-channel plate 159•14 has alarge number of channels, and further generates a large number ofelectron beams while the secondary electron beam made to form an imageby the electrostatic lenses 159•11 and 159•12 passes through thechannels. That is, the secondary electron beam is amplified. Thefluorescent screen 159•15 emits fluorescence having an intensityappropriate to the intensity of the secondary electron beam as theamplified secondary electron beam is applied. That is, the intensity ofthe secondary electron beam is converted into the intensity of light.The relay lens 159•16 is so situated as to guide the fluorescence to theimaging unit 159•17. The imaging unit 159•17 is constituted by a largenumber of imaging devices for converting light guided by the relay lens159•16 into an electric signal. So called a TDI detector is preferablyused to improve the S/N ratio of a detection signal. Furthermore, notonly the secondary electron beam but also the back-scattered electronbeam and the reflection electron beam are generated with irradiation ofthe primary electron beam, but these beams are collectively referred toas the secondary electron beam here.

A column 160•1 comprised of the mechanical structure of the A block andthe B block coupled thereto usually has one or more characteristicvibration modes. The resonance frequency and the resonance direction ofeach characteristic vibration mode are determined according to theshape, the weight distribution, the size, the layout of internalmachines and the like. For example, as shown in FIG. 160( b), the column160•1 has at least a mode 1 of characteristic vibrations 160•2. In thismode 1, the column 160•1 drifts at a frequency of 150 Hz approximatelyalong the Y direction, for example. One example of a transfer functionof the column in this case is shown in FIG. 161. In FIG. 161, thehorizontal axis represents the frequency, and the vertical axisrepresents the logarithm of vibration amplitude A. The transfer functionhas a gain of a resonance magnification of 30 dB (about a factor of 30)at a resonance frequency of 150 Hz. Thus, even if very small vibrationsare externally applied, frequency components at near 150 Hz areamplified by a factor of about 30 to vibrate the column if suchfrequency components are included in the vibrations. As a result, adetrimental event such as blurring of mapping is caused to occur.

To prevent such an event, the conventional technique takes large-scalemeasures such as placing the entire column on a vibration removal tableto remove external vibrations, and/or reconsidering the wall-thicknessand structure of the column to reduce the resonance magnification.

In this embodiment, to prevent the detrimental event, an actuator 160•4applying pressure vibrations 160•3 to the column so as to cancel out thevibrations 160•2 is placed in the base part of the block A as shown inFIG. 160( c). This actuator 160•4 is electrically connected to avibration attenuating circuit 159•18.

The outlined configurations of the actuator 160•4 and the vibrationattenuating circuit 159•18 are shown in FIG. 162. As shown in thisfigure, the actuator 160•4 has a piezoelectric element 162•4 having adielectric material 162•1 with a piezoelectric effect held betweenelectrodes 162•2 and 162•3, and a support base 162•5 fixed on thefixation base 159•2 for supporting the piezoelectric element from theelectrode 162•3 side. The piezoelectric element 162•4 is held betweenthe A block of the column 160•1 and the support base 162•5, theelectrode 162•2 is fixed to the outer wall of the A block, and theelectrode 162•3 is fixed to the support base 162•5. In this way, by thereciprocating vibrations 160•2, the piezoelectric element 162•4 receivesa positive pressure when the column 160•1 moves close to the element,and receives a negative pressure when the column moves away from theelement. The piezoelectric element 162•4 is situated at an effectiveposition for inhibiting the vibrations 160•2 of the column 160•1. Forexample, it is preferably situated so that the direction of thevibrations 160•2 is orthogonal to the electrodes 162•2 and 162•3.

The vibration attenuating circuit 159•18 is comprised of a variableinductance 162•6 and a resistance 162•7 connected in series between boththe electrodes 162•2 and 162•3 of the piezoelectric element 162•4. Sincethe variable inductance 162•6 has an inductance L, the resistance 162•7has a resistance value of R_(D), and the piezoelectric element 162•4 hasan electric capacitance of C, the piezoelectric element 162•4 and thevibration attenuating circuit 159•18 connected in series are equivalentto a series resonance circuit denoted by reference numeral 162•8. Theresonance frequency f₀′ of this series resonance circuit is expressed bythe following equation:f ₀′=1/{2π(LC)^(1/2)}.

In this embodiment, each parameter is set so that the resonancefrequency f₀′ of the series resonance circuit approximately equals theresonance frequency f₀ of the column 160•1. That is, the inductance L ofthe variable inductance 162•6 is adjusted so that the following equationholds for the electric capacitance C of the piezoelectric element 162•4:f ₀=1/2{2π(LC)^(1/2)}.

Actually, the capacitance C of the piezoelectric element 162•4 is smallin forming the resonance circuit according to the mechanical resonancefrequency, and hence a very large inductance L is often required but inthis case, a calculation amplifier or the like is used to formequivalently large inductance, whereby the resonance circuit can beachieved.

Furthermore, the value R_(D) of the resistance 162•7 is selected so thatthe Q value of a resonance frequency component of the series resonancecircuit approximately equals to the Q value of a resonance componenthaving a peak in the transfer function shown in FIG. 161. A seriesresonance circuit 162•8 created in this way has an electric frequencycharacteristic denoted by reference numeral 161•1 of FIG. 161.

The electron beam inspection apparatus 159•1 shown in FIG. 159 iscontrolled/managed by a control unit 159•19. The control unit 159•19 canbe constituted by a general personal computer or the like as shown inFIG. 159. This computer a control unit main body 159•20 carrying outvarious kinds of control and calculation operations according to apredetermined program, a CRT 159•21 displaying results of operations bythe main body, and input unit 159•22 such as a keyboard, a mouse and thelike for the operator to input instructions. Of course, the control unit159•19 may be constituted by hardware dedicated to the electron beaminspection apparatus, a workstation or the like.

The control unit main body 159•20 is constituted by a CPU, an RAM, anROM, a hard disk, various kinds of boards such as a video board and thelike (not shown). A secondary electron beam image storage area 159•23for storing electric signals received from the imaging unit 159•17, i.e.digital image data of secondary electron beam images of the wafer 159•6is assigned on a memory of the RAM or hard disk. Furthermore, areference image storage unit 159•24 for storing reference image data ofthe wafer having no defects in advance exists on the hard disk. Further,in addition to a control program for controlling the entire electronbeam inspection apparatus, a defect detection program 159•25 is storedon the hard disk. This defect detection program 159•25 has a function ofcontrolling the movement of the stage 159•10 in the XY plane, whilecarrying out various kinds of calculation operations such as additionfor digital image data received from the imaging unit 159•17, andreconstituting a secondary electron beam image on the storage area fromdata obtained as a result of the operations. Further, this defectdetection program 159•25 reads secondary electron beam image dataconstituted on the storage area 159•23, and automatically detectsdefects of the wafer 159•6 according to a predetermined algorithm basedon the image data.

The action of this embodiment will now be described. The primaryelectron beam is emitted from the electron beam source 159•3, andapplied to the surface of the set wafer 159•6 through the oblong opening159•4, quadrupole lens 159•5, the E×B deflector 159•7 and the objectivelens 159•9. As described above, an inspection subject area of, forexample, 100 μm×50 μm is illuminated on the wafer 159•6, and thesecondary electron beam is emitted. This secondary electron beam ismagnified and projected in the lower face of the multi-channel plate159•14 by the intermediate electrostatic lens 159•11 and the projectionelectrostatic lens 159•12, and imaged by the imaging unit 159•17 toobtain a secondary electron beam image of a projected area on the wafer159•6. By driving the stage 159•10 to move the wafer 159•6 successivelyby each predetermined width in the X-Y horizontal surface to carry outthe above procedures, whereby an image of the entire inspection surfacecan be obtained.

If an external force including a vibration component of the resonancefrequency f0 (150 Hz) is exerted on the column 160•1 while the enlargedsecondary electron beam image is formed, the column 160•1 amplifies thisvibration component with a resonance magnification (30 dB) determined bythe transfer function thereof and characteristically vibrates. Thevibrations 160•2 applies positive and negative pressures to thepiezoelectric element 162•4. The piezoelectric element 162•4 temporarilyconverts vibration energy of the column 160•1 into electric energy andoutputs the same. Since the inductance 162•6(L) and the resistance162•7(R_(D)) are connected in series to both the electrodes 162•2 and162•3 to a resonance circuit, the capacitive impedance of thepiezoelectric element 162•4 and the dielectric impedance L of theinductance 162•6 offset each other in the resonance frequency f0, andthe impedance of the resonance circuit is only the resistance R_(D) ineffect. Thus, during resonance, electric energy outputted from thepiezoelectric element 162•4 is almost fully consumed by the resistance162•7(R_(D)).

In this way, the piezoelectric element 162•4 produces a force so as tooffset an external force applied from the column 160•1 to thepiezoelectric element 162•4, and vibrations 160•2 produced by mechanicalresonance can be offset to increase the resonance magnification. Thesecondary electron beam is enlarged and mapped, and therefore a drift inmapping by vibrations is further increased but in this embodiment,blurring caused by this drift can be prevented before it occurs.

As shown in FIG. 163, the resonance component of the transfer function161•1 of the column 160•1 (corresponding to FIG. 161) as a mechanicalstructure is offset by the resonance component of the series resonancecircuit 162•8 having electric frequency characteristics 163•1, and thusthe column 160•1 has a total transfer function 163•2 having a lowresonance magnification as a whole.

As described above, when a satisfactory secondary electron beam imagefree from blurring in mapping is obtained, then the electron beaminspection apparatus 159•1 of this embodiment carries out processing forinspecting defects of the wafer 159•6 from the image. As defectinspection processing, so called a pattern matching method or the likemay be used. In this method, the reference image read from the referenceimage storage unit 159•24 is matched with the actually detectedsecondary electron beam image to calculate a distance value representingsimilarity between both the images. If the distance value is smallerthan threshold value, it is determined that the similarity is high todetermine “no defects exit”. On the other hand, if the distance value isequal to or greater than the predetermined threshold value, it isdetermined that the similarity is low to determine that “defects exist”.If it is determined that “defects exist”, it may be displayed forwarning the operator. At this time, the secondary electron beam image159•26 may be displayed on the display unit of the CRT 159•21.Furthermore, the pattern matching method may be used for each partialarea of the secondary electron beam image.

There is a defect inspection method shown in FIGS. 164 (a) to (c) otherthan the pattern matching method. In FIG. 164( a), an image 164•1 of adie detected first and an image 164•2 of another die detected second areshown. If it is determined that still an image of still another diedetected third is identical or similar to the first image 164•1, it isdetermined that an area 164•3 of the second die image 164•2 has defects,and thus the defect area can be detected.

In FIG. 164( b), an example of measurement of a line width of a patternformed on the wafer is shown. Reference numeral 164•6 denotes anintensity signal of an actual secondary electron beam when an actualpattern 164•4 on a wafer is scanned in a direction 164•5, and a width164•8 of an area in which this signal continuously exceeds a thresholdlevel 164•7 corrected and defined in advance can be measured as the linewidth of the pattern 164•4. If the line width measured in this way doesnot fall within a predetermined range, it can be determined that thepattern has defects.

In FIG. 164( c), an example of measurement of a potential contrast of apattern formed on a wafer is shown. In the configuration shown in FIG.159, an axisymmetric electrode 164•9 is provided above the wafer 159•6and, for example, a potential of −10 V is given to the electrode withrespect to the potential of the wafer of 0 V. The equipotential surfaceof −2 V at this time has a shape denoted by reference numeral 14•10.Here, patterns 164•11 and 164•12 formed on the wafer have potentials of−4 V and 0 V, respectively. In this case, a secondary electron beamemitted from the pattern 164•11 has a upward speed equivalent to kineticenergy of 2 eV on the −2 V equipotential surface 164•10, and thereforepasses over the potential barrier 164•10, and escapes from the electrode164•9 as shown in an orbit 164•13, and is detected by a detector. On theother hand, a secondary election beam emitted from the pattern 164•12cannot pass over the potential barrier of −2 V, and is forced back tothe wafer surface as shown in an orbit 164•14, and therefore is notdetected. Thus, the detection image of the pattern 164•11 is bright, andthe detection image of the pattern 164•12 is dark. In this way, apotential contrast is obtained. If the brightness and the potential ofthe detection image are corrected in advance, the potential of thepattern can be measured from the detection image. A defective area ofthe pattern can be evaluated from the potential distribution.

As described above, by making measurements described above for thesatisfactory secondary electron beam image free from blurring in mappingobtained from this embodiment, more accurate defect inspection can beachieved.

If the electron beam inspection apparatus described as this embodimentis used in wafer inspection steps in the device production process,degradation in the detection image due to vibrations of the mechanicalstructure can be prevented before it occurs, and therefore accurateinspection can be carried out effectively, thus making it possible toprevent defective products from being dispatched.

Furthermore, this embodiment is not limited to what has been describedabove, but may be altered arbitrarily and suitably in the spirit of thepresent invention. For example, not necessarily just one mechanicalresonance frequency and mode, but two or more mechanical resonancefrequencies and modes generally occur and in this case, they can becoped with by placing a necessary number of actuators 160•4 atappropriate positions in the column. For example, if the mechanicalstructure block A shown in FIG. 160( b) has not only vibrations 160•2 inthe Y direction but also vibrations in the X direction, a differentactuator may be placed so as to offset the vibrations in the Xdirection. Further, if the B block and the D block have independentcharacteristic vibrations, actuators may be placed for these blocks.

The vibration actuating circuit 159•18 is not necessarily equivalent tothe series resonance circuit 162•8, but may be matched with a circuithaving a plurality of resonance frequencies as electric frequencycharacteristics of the circuit if mechanical characteristic vibrationshave a plurality of resonance frequencies in the same vibrationdirection.

The location in which the actuator is placed is not limited to thecolumn, but the actuator can also be applied to parts required tocorrectly position the beam, for example the X-Y stage 159•10, oroptical parts of various kinds of optical instruments.

The semiconductor wafer 159•6 is used as an example of the inspectionsubject sample of the electron beam inspection apparatus of thisembodiment, but the inspection subject sample is not limited thereto,and any sample allowing defects to be detected with an electron beam canbe selected. For example, a mask or the like provided with a pattern forlight exposure for a wafer may be used as an inspection object.

Further, this embodiment may be generally applied to the electron beamirradiation apparatus irradiating a beam to a target position in amaterial. In this case, this embodiment may be applied not only to theapparatus carrying out inspection of the material but also extensivelyapplied to the apparatus carrying out any of processing, production andobservation thereof. Of course, the concept of the material refers notonly the wafer and the mask described above, but also any object capableof being subjected to at least any one of inspection, processing,production and observation with a beam. Similarly, the devicemanufacturing method may be applied not only to inspection during thestep of producing a semiconductor device, but also to a process itselffor producing the semiconductor device with the beam.

Furthermore, the configuration shown in FIG. 159 is shown as that of theelectron beam inspection apparatus of this embodiment, but theelectro-optical system and the like may be altered arbitrarily andsuitably. For example, the electron beam irradiating means of theelectron beam inspection apparatus 159•1 has a form of making a primaryelectron beam enter the surface of the wafer 159•6 at a right angle fromabove, but the E×B deflector 159•7 may be omitted to cause the primaryelectron beam enter the surface of the wafer 159•6 slantingly.

3-4) Embodiment for Wafer Holding

This embodiment relates to an electrostatic chuck adsorbing and holdinga wafer in an electrostatic manner in the electron beam apparatus, acombination of a wafer and an electrostatic chuck, particularly acombination of an electrostatic chuck and a wafer capable of being usedin an electron beam apparatus using a retarding-field objective lens,and a device production process using an electron beam apparatuscomprising an electrostatic chuck and a wafer.

A well known electrostatic chuck adsorbing and fixing a wafer in anelectrostatic manner, an electrode layer to be placed on a substrate isformed with a plurality of mutually insulated electrodes, and a powersupply apparatus applying voltages one after another from one electrodeto another electrode is provided. Furthermore, an electron beamapparatus using a retarding-field objective lens is well known.

If the wafer under process is evaluated by the electron beam apparatususing the retarding-field objective lens, it is necessary to apply anegative high voltage to the wafer. In this case, if the negative highvoltage is rapidly applied, the device under process may be broken, andtherefore the voltage should be gradually applied.

On the other hand, for most wafers, insulation films such as SiO₂ ornitride films are deposited on the side and back faces of the wafer, andtherefore a problem arises such that when a zero potential or lowpotential is to be given to the wafer, the voltage is not applied.Further, there is a problem such that a wafer raised at the centertoward the electrostatic chuck side can be relatively easily adsorbedand fixed, but a wafer recessed at the center toward the chuck side isheld with its edge portion chucked and its central portion not chuckedwith a unipolar electrostatic chuck.

To solve the above problems, this embodiment provides an electrostaticchuck capable of being used with the retarding-field objective lens,having the side and back faces covered with insulation films and capableof chucking the wafer recessed at the center toward the chuck side, anda combination of a wafer and an electrostatic chuck, and provides adevice production process for evaluating a wafer under process usingthis electrostatic chuck or combination of an electrostatic chuck andwafer.

FIG. 165 is a plan view of an electrostatic chuck 1410 in thisembodiment, showing an electrode plate 165•1 after removal of a wafer.FIG. 166 is a schematic sectional view in a vertical direction along theM-M line of the electrostatic chuck of FIG. 165, showing a state inwhich the wafer is placed and no voltage is applied. An electrostaticchuck 165•2 has a laminated structure comprised of a substrate 166•1, anelectrode plate 166•2 and an insulation layer 166•3 as shown in FIG.166. The electrode plate 166•2 includes a first electrode 165•2 and asecond electrode 165•3. The first electrode 165•2 and the secondelectrode 165•3 are separated from each other so that voltages can beseparately applied thereto, and they are made of thin film so that amovement can be made at a high speed without producing an eddy currentin a magnetic field.

The first electrode 165•2 is comprised of the central part and part ofthe periphery of the circular electrode plate 166•2 in the plan view,and the second electrode 165•3 is comprised of the rest horseshoeperipheral part of the electrode plate. The insulation layer 166•3 isplaced above the electrode plate 166•2. The insulation layer 166•3 ismade of a sapphire substrate having a thickness of 1 mm. Sapphire ismade of single crystals of alumina and has no pores unlike aluminaceramics, and therefore its insulation breakdown voltage is high. Forexample, the sapphire substrate having a thickness of 1 mm cansufficiently endure a difference in potential of 10⁴ V or greater.

A voltage is applied to a wafer 166•4 via a contact 166•5 having aknife-edged metal portion. As shown in FIG. 166, two contacts 166•5 aremade to contact the side face of the wafer 166•4. The reason why twocontacts 166•5 are used is that conduction may not be established ifonly one contact is used, and occurrence of a force of pushing the wafer166•4 toward one side should be avoided. An insulation layer (not shown)is broken to establish conduction, but because particles may bescattered when electrons are discharged, the contact 166•5 is connectedthrough a power supply 166•7 through a resistance 166•6 to preventoccurrence of a large discharge. If this resistance 166•6 is too large,no conduction hole is formed, and if the resistance 166•6 is too small,a large discharge occurs to cause particles to be scattered, andtherefore the allowable value of the resistance is determined for eachinsulation layer (not shown). This is because the thickness of theinsulation layer varies depending on the history of the wafer, and hencethe allowable value of the resistance should be determined for eachwafer.

FIG. 167( a) shows a time char of voltage application. A voltage of 4 kVis applied to the first electrode at a time of t=0 as shown by the lineA. A voltage of 4 kV is applied to the second electrode as shown by theline B at a time of t=t₀ when the central part and peripheral part ofthe wafer are both chucked. Control is performed so that a voltage C ofthe wafer is gradually deepened (reduced) at a time of t=t₁, and reaches−4 kV at a time t=t₂. The first and second electrodes have voltagesgradually reduced from a time of t=t₁ to a time of t=t₂, and it reaches0 V at a time t=t₂.

At a time t=t₃ when evaluation of the wafer adsorbed and held by thechuck is completed, the voltage C of the wafer reaches 0 V, and thewafer is taken to the outside.

If the electrostatic chuck adsorbs and holds the wafer with a differencein potential of only 2 kV instead of 4 kV, voltages A′ and B′ of 2 kVare applied to the first and second electrodes, respectively, as shownby the dash-dot in FIG. 167. When a voltage of −4 kV is applied to thewafer, voltages of −2 kV are applied to the first and second electrodes,respectively. In this way, through voltage application, application of avoltage to an insulation layer 2104 more than necessary can beprevented, thus making it possible to prevent breakage of the insulationlayer.

FIG. 168 is a block diagram showing an electron beam apparatuscomprising the electrostatic chuck described above. An electron beamemitted from an electron beam source 168•1 has an unnecessary beamremoved with an aperture of an anode 168•2 determining an aperture (NA),reduced by a condenser lens 168•7 and an objective lens 168•13, made toform an image on the wafer 166•4 having a voltage of −4 kV appliedthereto, and made to scan the wafer 166•4 by deflectors 168•8 and168•12. A secondary electron beam emitted from the wafer 166•4 iscollected by the objective lens 168•13, bent to the right at an angle ofabout 35° by an E×B separator 168•12, and detected with a secondaryelectron beam detector 168•10, and a SEM image on the wafer is obtained.In the electron beam apparatus of FIG. 168, reference numerals 168•3 and168•5 denote axis alignment devices, reference numeral 168•4 denotes anastigmatic correction device, reference numeral 168•6 denotes anaperture plate, reference numeral 168•11 denotes a shield, and referencenumeral 168•14 denotes an electrode. The electrostatic chuck describedwith FIGS. 166 and 167 is placed below the wafer 166•4.

By using this embodiment in inspection steps in the device productionprocess, a semiconductor device having a fine pattern can be inspectedin high throughput, and 100% inspection can be performed, thus making itpossible to improve the yield of products and prevent defective productsbeing from dispatched.

Furthermore, how the voltage applied to the electrostatic chuckincreases and decreases is not limited to the way shown in FIG. 167 (a).For example, the voltage may exponentially vary as shown in FIG. 167(b). It is only essential that the voltage should reach a predeterminedvoltage within certain time.

The first to twelfth embodiments of the present invention have beendescribed in detail above but in any of the embodiments, the term“predetermined voltage” means a voltage with which measurements such asinspection are carried out.

Furthermore, the embodiments described previously use electron beams ascharged particle beams, but the charged particle beam is not limitedthereto, and a charged particle beam other than an electron beam, or anon-charged particle beam such as a neutron beam having no charge, laserlight or an electromagnetic wave may be used.

Furthermore, when the charged particle beam apparatus according to thepresent invention is activated, a target material is caused to float andattracted to a high-pressure area by an adjacent interaction (charge ofparticles near the surface), and therefore organic materials aredeposited on various electrodes for use in formation and deflection ofthe charged particle beam. Organic materials gradually deposited as thesurface is charged badly affect mechanisms for forming and deflectingthe charged particle beam, and therefore these deposited organicmaterials must be removed periodically. Thus, to periodically remove thedeposited organic materials, it is preferable that using an electrodenear the area having the organic materials deposited thereon, plasmas ofhydrogen, oxygen or fluorine and HF, H₂O, C_(M)F_(N) and the likecontaining these elements are produced under vacuum, and a plasmapotential in a space is kept at a potential (several kilovolts, e.g. 20V to 5 kV) allowing sputter to occur on the electrode surface to removeonly organic materials by oxidization, hydrogenation and fluorination.

3-5) Embodiment of E×B Separator

FIG. 169 shows an E×B separator 169•1 of this embodiment. The E×Bseparator 169•1 is comprised of an electrostatic deflector and anelectromagnetic deflector, and is shown as a sectional view on the x-yplane orthogonal to the optical axis (axis perpendicular to the sheetface: z axis) in FIG. 169. The x axis direction and the Y axis directionare also orthogonal to each other.

The electrostatic deflector comprises a pair of electrodes(electrostatic deflection electrodes) 169•2 provided it a vacuumchamber, and generates an electric field E in the X axis direction. Theelectrostatic deflection electrodes 169•2 are attached to a vacuum wall169•4 of the vacuum chamber via an insulation spacer 169•3, and adistance D between these electrodes is set to a value smaller than alength 2L in the y axis direction of the electrostatic deflectionelectrode 169•2. By this setting, a range of uniform electric fieldintensity formed around the Z axis can be made to be relatively largebut ideally, as long as the requirement of D<L is met, the range ofuniform electric field intensity can be increased.

That is, since the range extending from the edge of the electrode to theposition of D/2 does not have a uniform electric field intensity, anarea of almost uniform electric field intensity is an area of 2L−D atthe central part excluding the end area that does not have a uniformelectric field. Accordingly, in order that there exist an area ofuniform electric field intensity, the requirement of 2L>D should be met,and by setting the requirement of L>D, the area of uniform electricfield intensity is further increased.

An electromagnetic deflector for generating a magnetic field M in the Yaxis direction is provided outside the vacuum wall 169•4. Theelectromagnetic deflector comprises an electromagnetic coil 169•5 and anelectromagnetic coil 169•6, and these coils generate magnetic fields inx axis and Y axis directions, respectively. Furthermore, a magneticfield M in the y axis direction can be generated with the coil 169•6alone, but a coil generating a magnetic field in the x axis direction isprovided for improving the orthogonality between the electric field andthe magnetic field M. That is, by canceling out a magnetic component inthe +x axis direction generated with the coil 169•6 by a magneticcomponent in the −x axis direction generated with the coil 169•6, theorthogonality between the electric field and the magnetic field can beimproved.

Since the coils 169•5 and 168•6 for generating magnetic fields areprovided outside the vacuum chamber, these coils are each divided intotwo parts, and they are attached from both sides of the vacuum wall1694, and fastened by screwing or the like in parts 169•7 to bond theparts together as one united body.

An outermost layer 169•8 of the E×B separator is constituted as a yokemade of permalloy or ferrite. The outermost layer 169•8 may be dividedinto two parts, and the divided parts may be attached to the outer faceof the coil 169•6 from both sides, and bonded together in the part 169•7by screwing or the like as in the case of the coils 169•5 and 169•6.

FIG. 170 shows a cross section orthogonal to the optical axis (z axis)of an E×B separator 170•1 of this embodiment. The E×B separator 170•1 ofFIG. 170 is different from the E×B separator of the embodiment shown inFIG. 169 in that six electrostatic deflection electrodes 170•1 areprovided. The electrostatic deflection electrodes 170•1 are eachsupplied with a voltage k·cos θ₁ (k is constant) proportional to cosθ_(i) where an angle between a line extending from the center of eachelectrode to the optical axis (z axis) and the direction of the electricfield (x axis direction) is θ_(i) (i=0, 1, 2, 3, 4, 5). The θ_(i) is anarbitrary angle.

In the embodiment shown in FIG. 170, only the electric field in the xaxis direction can be produced, and thus the coils 169•5 and 169•6 forgenerating the magnetic field in the y axis direction are provided tocorrect the orthogonality. According to this embodiment, the area ofuniform electric field intensity can be further increased compared withthe embodiment shown in FIG. 169.

In the E×B separators of the embodiments shown in FIGS. 169 and 170, thecoil for generating a magnetic field is formed as a saddle type, but atoroidal-type coil may be used.

In the E×B separator 169•1 of FIG. 169, since parallel flat plate-typeelectrodes in which the size along the direction perpendicular to theoptical axis is larger than the distance between electrodes are used asa pair of electrodes of the electrostatic deflector to generate anelectric field, the area in which a uniform-intensity and parallelelectric field is generated around the optical axis is increased.

Further, in the E×B separators of FIGS. 169 and 170, since saddle-typecoils are used for the electromagnetic deflector, and the angle betweenthe optical axis and the coil is set to 2π/3 on one side, no 3θ isgenerated and accordingly, the area in which a uniform-intensity andparallel electric field is generated around the optical axis isincreased. Furthermore, since the magnetic field is generated with theelectromagnetic coil, a deflection current can be superimposed on thecoil and accordingly, a scanning function can be provided.

The E×B separators of FIGS. 169 and 170 are each constituted as acombination of an electrostatic deflector and an electromagneticdeflector, and therefore by calculating the aberration of theelectrostatic deflector and the lens system, calculating the aberrationof the electromagnetic deflector and the lens system aside therefrom,and summing the aberrations, the aberration of the optical system can beobtained.

3-0 Embodiment of Production Line

FIG. 171 shows an example of a production line using the apparatus ofthe present invention. Information such as the lot number of a wafer tobe inspected by an inspection apparatus 171•1 and the history ofproduction apparatus involved in production can be read from a memoryprovided in an SMIF or FOUP 171•2, or the lot number can be recognizedby reading ID number of the SMIF, FOUP or wafer cassette. Duringtransportation of the wafer, the amount of water is controlled toprevent oxidization and the like of metal wiring.

The defect inspection apparatus 171•1 can be connected a network systemof the production line, and information such as the lot number of thewafer as an inspection subject and the results of inspection can be sentto a production line control computer 171•4 controlling the productionline, each production apparatus 171•5 and other inspection apparatus viathe network system 171•3. The production apparatuses includelithography-related apparatuses, for example, a light-exposureapparatus, a coater, a cure apparatus and a developer, or film formationapparatuses such as an etching apparatus, a spattering apparatus and aCVD apparatus, a CMP apparatus, various kinds of measurementapparatuses, other inspection apparatuses and a review apparatus.

3-7) Embodiment Using Other Electrons

The essential object of the present invention is to irradiate anelectron beam to a sample such as a substrate provided with a wiringpattern having a line width of 100 nm or smaller, and detect electronsobtaining information of the surface of the substrate, acquiring animage of the surface of the substrate from the detected electrons toinspect the sample surface. Particularly, the present invention proposesan inspection process and apparatus in which when the electron beam isapplied to the sample, an electron beam having an area including acertain imaging area is applied, electrons emitted from the imaging areaon the substrate are made to form an image using a CCD, CCD-TDI or thelike to acquire an image of the imaging area, and the obtained image isinspected with cell inspection and die comparison inspection combined asappropriate depending on the pattern of dies, whereby throughput muchhigher compared to the SEM process is achieved. That is, the inspectionprocess and inspection apparatus using an electron beam in the presentinvention solves both problems such that in an optical inspectionapparatus, defects of a pattern having a line width of 100 nm or smallercannot be sufficiently inspected due to a low resolution, and that in aSEM inspection apparatus, inspection requires too much time to meet therequirement of high throughput, thus making it possible to inspect awiring pattern having a line width of 100 nm or smaller in a sufficientresolution and high throughput.

In inspection of the sample, it is desirable in terms of the resolutionthat the electron beam is made to impinge upon the substrate, andelectrons emitted from the substrate are detected to obtain an image ofthe surface of the substrate. Thus, the examples of the presentinvention have been described mainly focusing on secondary electrons,reflection electrons and back-scattered electrons emitted from thesubstrate. However, electrons to be detected may be any electronsobtaining information of the surface of the substrate, and may be, forexample, mirror electrons (reflection electrons in a brad sense)reflected near the substrate instead of directly impinging upon thesubstrate by forming an inverse electric field near the substrate,transmission electrons passing through the substrate, or the like. Inparticular, use of mirror electrons has an advantage that the effect ofcharge-up is very small because electrons do not directly impinge uponthe sample.

In the case where mirror electrons are used, a negative potential lowerthan an accelerating voltage is applied to the sample to form an inverseelectric field near the sample. This negative potential is preferablyset to a value such that most electron beams are forced back near thesurface of the substrate. Specifically, it may be set at a potentialthat is 0.5 to 1.0 V or more lower than the acceleration voltage. Forexample, in the present invention, the voltage to be applied to thesample is preferably set to −4.000 kV to −4.050 kV if the acceleratingvoltage is −4 kV. It is more preferably set to −4.0005 kV to −4.020 kV,further more preferably −4.0005 kV to −4.010 kV.

Furthermore, in the case where transmission electrons are used, thevoltage to be applied to the sample is set to 0 to −4 kV, preferably 0to −3.9 kV, more preferably 0 to −3.5 kV if the accelerating voltage isset to −4 kV.

In addition, an X ray may be used instead of the electron beam. Thesecondary system and die comparison can be sufficiently applied.

Irrespective of which of mirror electrons or transmission electrons areused, the electron gun, the primary optical system, the deflector forseparating the primary electron beam from the detection electron beam,the detector using the CCD or CCD-TDI, the image processing apparatus,the calculation device for die comparison, and the like alreadydescribed are used. An election beam having a certain area such as anellipse is used, but a finely focused electron beam for use in a SEMtype may be used as a matter of course. One electron beam or two or moreelectron beams may be used as a matter of course. For the deflector forseparating the primary electron beam from the detection electron beam, aWien filter forming both electric and magnetic fields may be used, or adeflector forming only the magnetic field may be used. For the detector,a CCD or CCD-TDI capable of forming an imaging area on the detector tocarry out speedy inspection is used, but if a SEM-type electron gun isused, a semiconductor detector or the like corresponding to such a typeof electron gun is used as a matter of course. If an image of thesurface of the substrate is acquired, and comparison inspection of diesis carried out, cell inspection to be applied to a cyclic pattern andcomparison inspection of dies to be applied a random pattern are used asappropriated depending on the pattern of dies. Of course, onlycomparison inspection of dies may be carried out and in the case ofcomparison inspection of dies, a dies on the same substrate may becompared, or dies on different substrates may be compared, or the diemay be compared with CAD data. Suitable of them may be arbitrarily used.Further, the substrate is aligned before inspection. A positionaldeviation of the substrate is measured, and a deviation in rotationangle is corrected. At this time, a focus map may be created to carryout inspection while correcting the position of the substrate on theplane and a deviation in focus in consideration of the map duringinspection.

Furthermore, when the apparatus of the present invention is used inproduction steps, it is desirable that information of the wafer as aninspection object is acquired from a computer connected to the networksystem for controlling the production system, and inspection results aresent to incorporate the results in production conditions of apparatusesin the production line.

3-8) Embodiment Using Secondary Electrons and Reflection Electrons

This embodiment relates to a projection type electron beam apparatus ofhigh resolution and high throughput capable of irradiating an inspectionobject with a plane beam and switching between secondary electrons andreflection electrons depending on the inspection object. In this way,the type of irradiating an electron beam not to one spot on a sample butto a field of view extending at least two-dimensionally to form an imageof the field of view is called a “projection electron microscope type”.This projection-type electron beam apparatus is a high-resolution andhigh-throughput apparatus capable of avoiding a space charge effect,having a high signal-to-noise ratio and having an enhanced imageprocessing by parallel processing.

The implementation of the projection-type electron beam apparatus ofthis embodiment as a defect inspection apparatus will be described indetail below with reference to FIGS. 172 to 181. Furthermore, in thesefigures, like reference numerals or reference symbols denote identicalor corresponding components.

In FIGS. 172 (A) and (B), an electron gun EG of a defect inspectionapparatus EBI has a thermal electron beam emitting LaB₆ cathode 1capable of operating at a large current, and primary electrons emittedin a first direction from the electron gun EG pass through a primaryoptical system including several stages of quadrupole lenses 2 to havethe beam shape adjusted, and then pass through a Wien filter 172•1. Bythe Wien filter 172•1, the traveling direction of the primary electronsis changed to a second direction so that they enter a wafer W as aninspection object. The primary electrons exiting from the Wien filter172•1 and traveling in the second direction has the beam diameterlimited by an NA aperture plate 172•2, pass through an objective lens172•3, and are applied to the wafer W. The objective lens 172•3 is ahigh-accuracy electrostatic lens.

In this way, in the primary optical system, an electron gun of highluminance made of LaB₆ is used as the electron gun EG, thus making itpossible to obtain a primary beam having low energy, a large current anda large area compared to the conventional scanning defect inspectionapparatus.

Since the wafer W is irradiated with a plane beam with the cross-sectionformed into a rectangular shape of, for example, 200 μm×50 μm by theprimary optical system, a small area on the wafer W having apredetermined area can be irradiated. To irradiate the wafer W with thisplane beam, the wafer W is placed on a high-accuracy XY stage (notshown) coping with a 300 mm wafer, for example, and the XY stage istwo-dimensionally moved with the plane beam fixed. Furthermore, becauseit is not necessary to focus the primary electrons on a beam spot, theplane beam has a low current density, and thus the damage of the wafer Wis reduced. For example, the current density of the beam spot is 10³A/cm² in the conventional beam scanning defect inspection apparatus,while the current density of the plane beam is only 0.1 A/cm² to 0.01A/cm² in the defect inspection apparatus EBI shown in the figure. On theother hand, the dose is 1×10⁻⁵ C/cm² in the conventional beam scanningtype, while the dose is 1×10⁻⁴ C/cm² to 3×10⁻⁵ C/cm² in this type, andthis type of apparatus has a higher sensitivity.

Secondary electrons and reflection electrons are emitted from an area ofthe wafer irradiated with the plane beam-shaped primary electrons.Reflection electrodes will be described later and for explanation ofdetection of secondary electrons, first, the secondary electrons emittedfrom the wafer W, destined to travel in a direction opposite to thesecond direction, are enlarged by the objective lens 172•3, pass throughthe NA aperture plate 172•2 and the Wien filter 172•1, are enlargedagain by an intermediate lens 172•4, further enlarged by a projectionlens 172•5, and enters a secondary electron detection system D. In asecondary optical system guiding secondary electrons, the objective lens172•3, the intermediate lens 172•4 and the projection lens 172•5 are allhigh-accuracy lenses, and the secondary optical system is configured tohave a variable magnification. Because the primary electrons are made toenter the wafer W at almost a right angle, and the secondary electronsare taken out at almost a right angle, shading caused by irregularitieson the surface of the wafer does not occur.

The secondary electron detection system D receiving secondary electronsfrom the projection lens 172•5 comprises a micro-channel plate 172•6multiplying entering secondary electrons, a fluorescent screen 192•7converting the electrons exiting the micro-channel plate 172•6 intolight, and a sensor unit 172•8 converting the light emitting from thefluorescent screen 172•6 into an electric signal. The sensor unit 172•8has a high-sensitivity line sensor 172•9 constituted by a large numberof two-dimensionally arranged solid imaging devices, and fluorescenceemitted from the fluorescent screen 172•7 is converted into an electricsignal by the line sensor 172•9, sent to an image processing unit172•10, and processed in parallel, in multiple stages and at a highspeed.

While the wafer W is moved to irradiate and scan individual areas on thewafer W with a plane beam one after another, the image processing unit172•10 accumulates data about XY coordinates and images of areasincluding defects, and creates an inspection result file includingcoordinates and images of all areas of an inspection object includingdefects for one wafer. In this way, inspection results can becollectively managed. When this inspection result file is read out, adefect distribution and a defect detail list of the wafer is displayedon a display of the image processing unit 172•10.

In fact, of various components of the defect inspection apparatus EBI,the sensor unit 172•8 is placed in the atmosphere, but other componentsare placed in a column kept under vacuum and therefore, in thisembodiment, a light guide is provided on an appropriate wall surface ofthe column, so that light exiting from the fluorescent screen 172•7 istaken out into the atmosphere through the light guide, and passed to theline sensor 172•9.

FIG. 173 shows a specific example of the configuration of the secondaryelectron detection system D in the defect inspection apparatus EBI ofFIG. 172. A secondary electron image or reflection electron image 173•1is formed on the entrance surface of the micro-channel plate 172•6 bythe projection lens 172•5. The micro-channel plate 172•6 has, forexample, a resolution of 16 μm, a gain of 10³ to 10⁴ and 2100×520, andmultiplies electrons according to the formed electron image 173•1 toirradiate the fluorescent screen 172•7. Consequently, fluorescence isemitted from an area of the fluorescent screen 172•7 irradiated withelectrons, and the emitted fluorescence is discharged into theatmosphere through the light guide 173•2 of low deformation (e.g. 0.4%).The emitted fluorescence is made to enter the line sensor 172•9 throughan optical relay lens 173•3. For example, the optical relay lens 173•3has a magnification of ½, a transmittance of 2.3% and a deformation of0.40%, and the line sensor 172•9 has a pixel number of 2048×512. Theoptical relay lens 173•3 forms an optical image 173•4 matching theelectron image 173•1 on the entrance surface of the line sensor 172•9.An FOP (fiber optic plate) may be used instead of the light guide 173•2and the relay lens 173•3 and in this case, the magnification is 1×.

The defect inspection apparatus EBI shown in FIG. 172 can be operated inone of a positive charge mode and a negative charge mode, in the case ofsecondary electrons, by adjusting an accelerating voltage of theelectron gun EG and a wafer electrode applied to the wafer W and usingthe electron detection system D. Further, by adjusting the acceleratingvoltage of the electron gun EG, the wafer voltage applied to the wafer Wand objective lens conditions, the defect inspection apparatus EBI canbe operated in a reflection electron imaging mode to detect reflectionelectrodes of high energy emitted from the wafer W with irradiation ofprimary electrons. Since reflection electrodes have energy equal toenergy of the primary electrons entering a sample such as the wafer W,and thus have energy higher than that of secondary electrons, thereflection electrodes are hard to be influenced by a potential such ascharge of the surface of the sample. For the electron detection system,an electron impact detector such as an electron impact CCD or electronimpact TDI outputting an electric signal matching the intensity ofsecondary electrons or reflection electrons may be used. In this case,the micro-channel plate 172•6, the fluorescent screen 172•7 and therelay lens 173•3 (or FOP) are not used, but the electron impact detectoris placed at an image formation position and used. This configurationenables the defect inspection apparatus EBI to operate in a modesuitable for an inspection object. For example, the negative charge modeor reflection electron imaging mode may be used for detecting defects ofmetal wiring, defects of gate contact (GC) wiring or defects of a resistpattern, and the reflection electron imaging mode may be used to detectpoor conduction of a via, or residues on the bottom of the via afteretching.

FIG. 174 (A) illustrates requirements for operating the defectinspection apparatus EBI of FIG. 1 in the three modes described above.The accelerating voltage of the electron gun EG is V_(A), the wafervoltage applied to the wafer W is V_(W), the irradiation energy ofprimary electrons when the wafer W is irradiated is E_(IN), and thesignal energy of secondary electrons entering the electron detectionsystem D is E_(OUT). The electron gun EG is configured so that theaccelerating voltage V_(A) is variable, and the variable wafer voltageV_(W) is applied to the wafer W from an appropriate power supply (notshown). Then, if the accelerating voltage V_(A) and the wafer voltageV_(W) are adjusted, and the electron detection system D is used, thedefect inspection apparatus EBI can operate in the positive charge modein the range of the secondary electron yield greater than 1, and canoperate in the negative mode in the range of the secondary electronyield smaller than 1 as shown in FIG. 174(B). Furthermore, by adjustingthe accelerating voltage V_(A), the wafer voltage V_(W) and theobjective lens conditions, the defect inspection apparatus EBI canoperate in the reflection electron imaging mode using a difference inenergy between secondary electrons and reflection electrons.Furthermore, in FIG. 174(B), in fact, the value of electron irradiationenergy E_(IN) at the boundary between the positive charge area and thenegative charge area varies depending on the sample.

One example of values of V_(A), V_(W), E_(IN) and E_(OUT) for operatingthe defect inspection apparatus EBI in the reflection electron imagingmode, the negative charge mode and the positive charge mode is describedbelow.

Values in Reflection Electron Imaging Mode:

V_(A)=−4.0 kV;

V_(W)=−2.5 kV;

E_(IN)=1.5 keV; and

E_(OUT)=4 keV.

Values in Negative Charge Mode:

V_(A)=−7.0 kV;

V_(W)=−4.0 kV;

E_(IN)=3.0 keV; and

E_(OUT)=4 keV+α (α=energy width of secondary electrons).

Values in Positive Charge Mode:

V_(A)=−4.5 kV;

V_(W)=−4.0 kV;

E_(IN)=0.5 keV; and

E_(OUT)=4 keV+α (α=energy width of secondary electrons).

In fact, the detection amounts of secondary electrons and reflectionelectrons vary depending on the surface composition of the inspectionsubject area on the wafer W, the pattern shape and the surfacepotential. That is, the yield of secondary electrons and the amount ofreflection electrons vary depending on the surface composition of theinspection subject on the wafer W, and the yield of secondary electronsand the amount of reflection electrons are larger at pointed sites andcorners than in plane areas. Furthermore, if the surface potential ofthe inspection subject on the wafer W is high, the amount of emittedsecondary electrons decreases. In this way, the intensities of electricsignals obtained from secondary electrons and reflection electronsdetected by the detection system D vary depending on the material, thepattern shape and the surface potential.

FIG. 175 shows the shape of the cross-section of each electrode of theelectrostatic lens for use in the electro-optical system of the defectinspection apparatus EBI shown in FIG. 172. As shown in FIG. 175, thedistance between the wafer W and the micro-channel plate 172•6 is, forexample, 800 mm, and the objective lens 172•3, the intermediate lens172•4 and the projection lens 172•5 are electrostatic lenses each havinga plurality of electrodes having specific shapes. Now, if a voltage of−4 kV is applied to the wafer W, a voltage of +20 kV is applied to anelectrode of the objective lens 172•3, which is closest to the wafer W,and a voltage of −1476 V is applied to other electrodes. At the sametime, a voltage of −2450 V is applied to the intermediate lens 172•4,and a voltage of −4120 V is applied to the projection lens 172•5. As aresult, the magnification obtained with the secondary optical system is2.4 with the objective lens 172•5, 2.8 with the intermediate lens 172•4,and 37 with the projection lens 172•5, resulting in total 260.Furthermore, in FIG. 175, reference numerals 175•1 and 175•2 denotefield apertures for limiting the beam diameter, and reference numeral175•3 denotes an deflector.

FIG. 176(A) schematically shows the configuration of amulti-beam/multi-pixel-type defect inspection apparatus EBI that isanother embodiment of a projection type electron beam apparatus. Anelectron gun EGm in this defect inspection apparatus is amulti-beam-type electron gun having a LaB₆ cathode and capable ofemitting a plurality of primary electron beams 176•1. The primaryelectron beams 176•1 have beam diameters adjusted by an aperture plate176•2 provided with pores at positions corresponding to the primaryelectron beams, then have beam positions adjusted by two-stageaxisymmetric lenses 176•3 and 176•4, travel in a first direction, passthrough the Wien filter 172•1, change the traveling direction from thefirst direction to a second direction, and travel so as to enter thewafer W. Thereafter, the primary electron beams 176•1 pass through theNA aperture plate 172•2 and the objective lens 172•3, and are applied topredetermined areas of the wafer W.

Secondary electrodes and reflection electrodes 176•5 emitted from thewafer W with irradiation of the primary electron beams 176•1 travel in adirection opposite to the second direction to pass through the objectivelens 172•3, the NA aperture plate 172•2, the Wien filter 172•1, theintermediate lens 172•4 and the projection lens 172•5, enters thedetection system D, and is converted into an electric signal by thesensor unit 172•8 in the same manner as described with FIG. 172(A).

A deflector 176•6 for deflecting the primary electron beams 176•1 isplaced between the axisymmetric lens 176•4 situated on the downstreamside when seen from the electron gun EGm and the Wien filter 172•1. Toscan a certain area R on the wafer W with the primary electron beams176•1, the primary electron beams 176•1 are deflected in the x axisdirection perpendicular to the Y axis at a time by the deflector 176•6while the wafer W is moved in the Y axis as shown in FIG. 176 (B). Inthis way, the area R is raster-scanned with the primary electron beams176•1.

FIG. 177(A) shows the outlined configuration of amulti-beam/mono-pixel-type defect inspection apparatus EBI that is stillanother embodiment of a projection type electron beam apparatus. In thisfigure, the electron gun EGm can emit a plurality of primary electronbeams 176•1, and the emitted primary electron beams 176•1 are guided bythe aperture plate 176•2, the axisymmetric lenses 176•3 and 176•4, thedeflector 176•6, the Wien filter 172•1 and the objective lens 172•3 soas to travel in the first direction, and are applied to the wafer W inthe same manner as described with FIG. 176(A).

Secondary electrons or reflection electrons 176•5 emitted from the waferW with irradiation of the primary electron beams 176•1 pass through theobjective lens 172•3, then have the traveling direction changed by apredetermined angle by the Wien filter 172•1, then pass through theintermediate lens 172•4 and the projection lens 172•5, and enter amulti-detection system D′. The multi-detection system D′ in this figureis a secondary electron detection system, and comprises a multi-apertureplate 177•1 provided with pores identical in number to n pores formed inthe aperture electrode 176•2, n detectors 177•2 provided incorrespondence with the pores of the multi-aperture plate 177•1 so thatsecondary electrons passing through the n pores of the aperture plate177•1 are captured and converted into electric signals indicating theintensity of the secondary electrons, n amplifiers 177•3 amplifying theelectric signals outputted from the detectors 177•2, and an imageprocessing unit 172•10′ converting into digital signals the electricsignals amplified by the amplifiers 177•3, and performing storage,display, comparison and the like of image signals of an scan subjectarea R on the wafer W.

In the defect inspection apparatus EBI shown in FIG. 177(A), the area isscanned with the primary electron beams 176•1 in a manner as shown inFIG. 177(B). That is, as shown in FIG. 177 (B), the area R is divided inthe Y axis direction by the number of primary electron beams 176•1 intosub-areas, for example, r1, r2, r3 and r4, and each of the primaryelectron beams 176•1 is assigned to each of the sub-areas r1 to r4.Then, the primary electron beams 176•1 are deflected in the X axisdirection at a time by the deflector 176•6 while the wafer W is moved inthe Y axis direction to scan the sub-areas r1 to r4 with the primaryelectron beams 176•1. In this way, the area R is scanned with theprimary electron beams 176•1.

Furthermore, the primary optical system of the multi-beam is not limitedto that of FIG. 176, but it is only essential that the beam should be amulti-beam at the time when it is applied to the sample and, forexample, a single electron gun may be used.

In the defect inspection apparatus EBI described above, a mechanismcapable of placing the wafer W on a stage and positioning the stageaccurately in a vacuum chamber is preferably used. To accuratelyposition the stage, for example, a structure in which the stage issupported by a static-pressure bearing in a non-contact manner isemployed, hi this case, in order that high-pressure gas supplied fromthe static-pressure bearing is not discharged into the vacuum chamber,it is desirable that a differential exhaust mechanism discharginghigh-pressure gas is formed in the area of the static-pressure bearingto maintain the degree of vacuum of the vacuum chamber.

FIG. 178 shows one example of the configuration of a mechanism foraccurately positioning a stage holding the wafer W in a vacuum chamber,and a circulation piping system of inert gas. In FIG. 178, the leadingend portion of a column 178•1 irradiating primary electrons to the waferW, i.e. a primary electron irradiating portion 178•2 is attached to ahousing 178•3 sectioning a vacuum chamber C. The wafer W placed on amovable table in the X direction (lateral direction in FIG. 178) of ahigh-accuracy XY stage 178•4 is placed just below the column 178•1. Bymoving the XY stage 178•4 in X and Y directions (direction perpendicularto sheet face in FIG. 178), primary electrons can be correctlyirradiated with respect to any position on the surface of the wafer W.

A seat 178•5 of the XY stage 178•4 is fixed on the bottom wall of thehousing 178•3, and a Y table 178•6 moving in the Y direction is placedon the seat 178•5. Raised portions are formed on both side faces of theY table 178•6 (left and right side faces in FIG. 178), and the raisedportions fit into a pair of recessed grooves formed on a pair of Ydirection guides 178•7 a and 178•7 b provided on the seat 178•5. Therecessed grooves extend in the Y direction over almost the full lengthsof the Y direction guides 178•7 a and 178•7 b. Static-pressure beatings(not shown) each having a well known structure are provided on the upperand lower faces and the side faces of the raised portions protrudinginto the recessed grooves. By blowing high-pressure and high-purityinert gas (N2 gas, Ar gas, etc.) via the static-pressure bearings, the Ytable 178•6 is supported on the Y direction guides 178•7 a and 178•7 bin a non-contact manner, and can make a reciprocating motion.Furthermore, a linear motor 178•8 having a well known structure isplaced between the seat 178•5 and the Y table 178•6 for driving the Ytable 178•6 in the Y direction.

On the upper side of the Y table 178•6, an X table 178•9 is placed insuch a manner that it can move in the X direction. A pair of X directionguides 3178•10 a and 178•10 b (only X direction guide 178•10 a is shownin FIG. 178) identical in structure to the Y direction guides 178•7 aand 178•7 b for the Y table 178•6 are provided in such a manner as tosurround the X table 178•9. Recessed grooves are formed on the sides ofthe X direction guides facing the X table 178•9, and raised portionsprotruding into the grooves are formed on the side parts of the X table178•9 facing the X direction guides. These recessed grooves extend overthe full lengths of the X direction guides. Static-pressure bearings(not shown) similar to the static-pressure bearings for supporting the Ytable 178•6 in a non-contact manner are provided on the upper and lowerfaces and side faces of the raised portions of the X direction table178•9 protruding into the recessed grooves. By supplying high-pressureand high-purity inert gas to the static-pressure bearings to blow theinert gas from the static-pressure bearings to the guide surfaces of theX direction guides 178•10 a and 178•10 b, the X table 178•9 isaccurately supported on the X direction guides 178•10 a and 178•10 b ina non-contact manner. A linear motor 178•11 having a well knownstructure is placed on the Y table 178•6 for driving the X table 178•9in the X direction.

Since a stage mechanism with static-pressure bearings that is used inthe atmosphere can be directly used as the XY stage 178•4, an XY stageequivalent in accuracy in to an high-accuracy stage for the atmospherefor use in a light-exposure apparatus or the like can be achieved as anXY stage for defect inspection apparatus at almost the same cost and inalmost the same size. Furthermore, the wafer W is not placed directly onthe X table 178•9, but is usually placed on a sample table having afunction of detachably holding the wafer W and changing the position bya small amount with respect to the XY stage 178•4.

The inert gas is supplied to the static-pressure bearings throughflexible tubes 178•12 and 178•13 and a gas channel (not shown) formed inthe XY stage 178•4. The high-pressure inert gas supplied to thestatic-pressure bearings are blown into gaps of several microns andseveral tens of microns formed between the static-pressure bearings andthe opposite guide surfaces of the Y direction guides 178•7 a and 1878•7b and the X direction guides 178•10 a and 178•10 b to correctly positionthe Y table 178•6 and the X table 178•9 in the X direction, Y directionand Z direction (vertical direction in FIG. 178) with respect to theguide surfaces. Gas molecules of the inert gas blown from thestatic-pressure bearings diffuse into the vacuum chamber C, and aredischarged through exhaust ports 178•14, 178•15 a and 178•15 b andvacuum tubes 178•16 and 178•17 by a dry vacuum pump 178•18. The seat178•5 is cut through so that the suction ports of the exhaust ports178•15 a and 178•15 b are provided on the upper face of the seat 178•5.In this way, the suction ports are situated near the position at whichthe high-pressure is discharged from the XY stage 178•4, thus preventingthe pressure within the vacuum chamber C from being increased by thehigh-pressure gas blown from the static-pressure bearings.

The exhaust port of the dry vacuum pump 178•18 is connected to acompressor 178•20 through a tube 178•19, and the exhaust port of thecompressor 178•20 is connected to the flexible tubes 178•12 and 178•13through tubes 178•21, 178•22, 178•23 and regulators 178•24 and 178•25.Accordingly, inert gas discharged from the dry vacuum pump 178•18 iscompressed again by the compressor 178•20, adjusted to have anappropriate pressure by the regulators 178•24 and 178•25, then suppliedagain to the static-pressure bearings of the XY table. In this way,high-purity inert gas is circulated and reused, thus making it possibleto save inert gas, and no inert gas is emitted from the defectinspection apparatus EBI, thus making it possible to prevent an accidentsuch as suffocation with inert gas. Furthermore, removal means 178•26such as a cold trap or filter is preferably provided at some midpoint inthe tube 178•21 on the discharge side of the compressor 178•20, so thatimpurities such as water and oil entering the circulating gas aretrapped and prevented from being supplied to the static-pressurebearings.

A differential exhaust mechanism 178•27 is provided around the leadingend portion of the column 178•1, i.e. the primary electron irradiatingportion 178•2. This is intended to keep the pressure of a primaryelectron beam irradiation space 178•28 at a sufficiently low level evenif the pressure within the vacuum pump is high. A ring member 178•29 ofthe differential exhaust mechanism 178•27 provided around the primaryelectron irradiating portion 178•2 is positioned with respect to thehousing 178•3 so that a very small gap of several microns to severaltens of microns is formed between the lower face of the ring member(face opposite to the wafer W) and the wafer W.

A ring groove 178•30 is formed in the lower face of the ring member178•29, and the ring groove 178•30 is connected to an exhaust port178•31. The exhaust port 178•31 is connected to a turbo-molecular pump178•33 being an ultra-high vacuum pump through a vacuum tube 178•32.Furthermore, an exhaust port 178•34 is provided at an appropriatelocation in the column 178•1, and the air exhaust port 178•34 isconnected to a turbo-molecular pump 178•36 through a vacuum tube 178•35.The turbo-molecular pumps 178•33 and 178•36 are connected to the dryvacuum pump 178•18 by vacuum tubes 178•37 and 178•38. Thus, gasmolecules of inert gas entering the differential exhaust mechanism178•27 and the charged electron beam irradiation space 178•26 aredischarged through the ring groove 178•30, the exhaust port 178•31 andthe vacuum tube 178•32 by the turbo-molecular pump 178•33, and thereforegas molecules entering the space 178•28 surrounded by the ring member178•29 from the vacuum chamber C. In this way, the pressure within theprimary electron irradiation space 178•28 can be kept at a low level,thus making it possible to apply primary electrons without any problems.Furthermore, gas molecules suctioned from the leading end portion of thecolumn 178•1 are discharged through the air exhaust port 178•34 and thevacuum tube 178•35 by the turbo-molecular pump 178•36. The gas moleculesdischarged from the turbo-molecular pumps 178•33 and 178•36 arecollected by the dry vacuum pump 178•18 and supplied to the compressor178•20.

Furthermore, the ring groove 178•30 may have a double or triplestructure depending on the pressure within the vacuum chamber C or thepressure within the primary electron irradiation space 178•28.Furthermore, in the inspection apparatus shown in FIG. 178, one dryvacuum pump is used for the roughing vacuum pump of the turbo-molecularpump and the pump for evacuating the vacuum chamber, but the chamber maybe evacuated with dry vacuum pumps of different lines depending on theflow rate of high-pressure gas supplied to the static-pressure bearingof the XY stage, the volume and inner surface area of the vacuumchamber, the inner diameter and length of the vacuum tube and the like.

Dry nitrogen is generally used as high-pressure gas supplied to thestatic-pressure bearing of the XY stage 178•4. If possible, however,inert gas of higher purity is preferably used. This is because ifimpurities such as water and oil are contained in the gas, molecules oftheses impurities are deposited on the inner surface of the housing178•3 sectioning the vacuum chamber C and the surfaces of the stagecomponents to reduce the degree of vacuum, or deposited on the surfaceof the wafer W to reduce the degree of vacuum of the primary electronirradiation space 178•28. Furthermore, since it is necessary to preventthe situation in which the gas contains water and oil where possible,the turbo-molecular pumps 178•33 and 178•36, the dry vacuum pump 178•18and the compressor 178•20 are each required to have a structure suchthat no water and oil enters the gas channel.

Furthermore, as shown in FIG. 178, a high-purity inert gas supply systemis connected to the circulation piping system of inert gas, and plays arole to fill high-purity inert gas in the vacuum chamber C and allcirculation systems including the vacuum tubes 178•16, 178•15, 178•32,178•35 and 178•37 and the pressure tubes 178•19, 178•21, 178•22, 178•23and 178•39 when circulation of gas is started, and a role to supply anamount of gas equivalent to a shortfall in case where a flow rate ofcirculating gas drops for some cause. Furthermore, by imparting to thedry vacuum pump 178•18 a function of compression to an atmosphericpressure or higher, the dry vacuum pump 178•18 can be made to serve alsoas the compressor 178•20. Further, instead of the turbo-molecular pump178•36, a pump such as an ion pump or getter pump can be used as anultra-high vacuum pump for use in evacuation of the column 178•1.However, if such an entrapment pump is used, a circulation piping systemcannot be built. Instead of the dry vacuum pump 178•18, a different typeof dry pump such as diaphragm-type dry pump may be used.

FIG. 179 shows examples of values of the sizes of the ring member 178•29of the differential exhaust mechanism 178•27 and the ring groove 178•30formed thereon. Here, double ring grooves isolated from each other in aradial direction are provided. The flow rate supplied to thestatic-pressure bearing is usually about 20 L/min (equivalent inatmospheric pressure). Provided that the vacuum chamber C is evacuatedwith a dry pump having a pumping speed of 20000 L/min through a vacuumtube having an inner diameter of 50 mm and a length of 2 m, the pressurewithin the vacuum chamber is about 160 Pa (about 1.2 Torr). At thistime, if the sizes of the differential exhaust mechanism 178•27, thering member 178•29, the ring groove 178•30 and the like are set as shownin FIG. 179, the pressure within a primary electron irradiation space 56can be kept at 10⁻⁴ Pa (10⁻⁶ Torr).

FIG. 180 schematically shows the overall configuration of an inspectionsystem having the defect inspection apparatus EBI described with FIGS.172 to 179. As shown in the figure, components on the route ranging fromthe primary optical system of the defect inspection apparatus EBIthrough the wafer W and the secondary optical system to the detectionsystem D are housed in the column 178•1 exhibiting a magnetic shieldfunction, and the column 178•1 is placed on the upper face of avibration removal table 180•1 supported by an active vibration removalunit so as to prevent transfer of vibrations from outside. The inside ofthe column 178•1 is kept under vacuum by a vacuum pumping system 180•2.A necessary voltage is supplied from a control power supply 180•3through a high-pressure cable 180•4 to components of the primary opticalsystem and the secondary optical system in the column 178•1.

An alignment mechanism 180•5 comprising an optical microscope andauto-focusing means is provided at an appropriate location in the column178•1 to place components constituting the primary optical system andthe secondary optical system on predetermined optical axes and make anadjustment so that primary electrons emitted from the electron gunautomatically come into a focus on the wafer W.

The XY stage 178•4 comprising a chuck (not shown) for placing and fixingthe wafer W is provided on the upper face of the vibration table 180•1,and the position of the XY stage 178•4 during a scan period is detectedat predetermined intervals by a laser interferometer. Further, a loader180•6 for accumulating a plurality of wafers W as inspected objects, anda transportation robot 180•7 for holding the wafer in the loader 180•6and placing the wafer W on the XY stage 178•4 in the column 178•1, andtaking the wafer W from the column 178•1 after inspection are placed onthe upper face of the vibration removal table 180•1.

The operation of the overall system is controlled by a main controller180•8 in which necessary programs are installed. The main controller180•8 comprises a display 180•9, and is connected to the detectionsystem D through a cable 180•10. Consequently, the main controller 180•8can receive a digital image signal from the detection system D throughthe cable 180•10 to process the signal with the image processing unit172•10, and display the contents of an inspection result file obtainedby the scanning of the wafer W, a defect distribution of the wafer W andthe like on the display 180•9. Furthermore, the main controller 180•8displays an operation state of the system on the display 180•9 tocontrol the operation of the overall system.

Furthermore, in the above description, the stage holding the wafer W ismovable in the XY plane, but in addition thereto, the stage may berotatable about any axis perpendicular to the XY plane or extendingpassing the XY plane. Furthermore, the inspection object is not limitedto a wafer, but any sample capable of being inspected with an electronbeam, such as a mask, is included as an inspected object. Further, bymutually connecting the projection-type electron beam apparatus in thisembodiment, a beam scanning defect review apparatus, a server and themain controller through a IAN, a distributed defect inspection networkcan be built.

As apparent from the above description, this embodiment exhibits thefollowing remarkable effects.

(1) Because the sample is irradiated with a plane beam, throughput canbe improved to the extent that for example, defect inspection time perwafer can be reduced by a factor of 7 compared to the conventional beamscanning inspection apparatus.

(2) A space charge effect can be avoided because it is not necessary tofocus primary electrons on a beam spot, and the sample is notsignificantly damaged because the sample is irradiated in a low currentdensity.

(3) Because the sample is irradiated with a plane beam, inspection canbe performed for a size smaller than one pixel.

(4) By selecting an accelerating voltage of the electron gun and avoltage applied to the sample, and adjusting an objective lens, theapparatus can be operated in any one of a positive charge mode, anegative charge mode and a reflection electron imaging mode, thus makingit possible to perform appropriate inspection according to theinspection site in the sample.(5) By using an electrostatic lens, the primary optical system and/orthe secondary optical system can be downsized and improved in accuracy.

What is claimed is:
 1. A method of inspecting a substrate having diesarranged in matrix, wherein the substrate is irradiated by primaryelectrons and secondary electrons generated from the substrate isdetected by a detector, the method comprising: (a) placing the substrateon a stage; (b) selecting a reference die from among the dies placed onthe stage to obtain a pattern matching template image including featurecoordinates of the reference die; (c) performing pattern matching withan arbitrary die in a row or column including the reference die usingthe template image to obtain feature coordinates of the arbitrary die;(d) calculating an angle of misalignment between the direction of therow or column including the reference die and one of the directions ofmovement of the substrate on the basis of the feature coordinates of thearbitrary die and those of the reference die; (e) rotating the stage tocorrect the angle of misalignment to conform the direction of the row orcolumn including the reference die with the one of the directions ofmovement of the substrate; (f) after step (e), rotating the detector toconform the one of the directions of movement of the substrate with adirection of scan of the detector; and (g) after step (f), irradiate thesubstrate with the primary electrons.
 2. The method of claim 1, furthercomprising: prior to step (a), disposing means for irradiating thesubstrate with electrons, the stage and the detector within a vacuumcontainer, wherein step (f) is performed by a rotation mechanismdisposed outside of the vacuum container.
 3. The method of claim 2,wherein the vacuum container comprises a first barrel and a secondbarrel rotatably supported against the first barrel and having thedetector and wherein the rotation mechanism is structured to rotate thesecond barrel.
 4. The method of claim 1, wherein steps (a)-(g) areperformed in a projection mapping type electron beam apparatus wherein aprimary electron beam having two-dimensional cross section irradiatesthe substrate to detect by the detector a secondary electron beam havinginformation of a surface of the substrate.
 5. The method of claim 4,wherein the electron beam apparatus comprises a beam separator (E×B) andwherein the direction of electric field of the E×B is conformed with thedirection of scan of the detector.
 6. The method of claim 5, furthercomprising: after step (e) and prior to step (f), moving a numericalaperture (NA) device to an optically optimum position in accordance witha change in magnification of the electron beam apparatus.
 7. The methodof claim 2, wherein steps (a)-(g) are performed using an opticalmicroscope having a high magnification after steps (a)-(g) are performedusing an optical microscope having a low magnification.
 8. The method ofclaim 1, wherein step (b) comprises repeatedly performing: estimatingfeature coordinates of a next arbitrary die on the basis of a positionalrelation between the feature coordinates of the reference die andaccurate feature coordinates of the arbitrary die obtained by thepattern matching of the template image; performing pattern matchingusing the template image near the estimated feature coordinates; andobtaining accurate feature coordinates of the next arbitrary die.
 9. Themethod of claim 8, wherein the repeatedly performing comprises:repeatedly estimating the feature coordinates of the next arbitrary dieon the basis of a positional relation between the feature coordinates ofthe reference die and the feature coordinates of the die obtained in thestep just before.
 10. The method of claim 1, further comprising:obtaining a size in the direction perpendicular to the row or columnused for obtaining the angle of displacement; and producing a die map onthe basis of the obtained size.
 11. The method of claim 10, wherein theobtaining a size comprises: selecting a reference die to obtain apattern matching template image including feature coordinates of thereference die; performing pattern matching, using the template image, toan arbitrary die located on a row or column in a direction perpendicularto the row or column based on which the angle of displacement isobtained to obtain feature coordinates of the arbitrary die; andobtaining a distance between the feature coordinates of the referencedie and those of the arbitrary die and the number of dies includedwithin the distance to obtain a size of a die in a directionperpendicular to the row or column based on which the angle ofdisplacement is obtained.
 12. The method of claim 1, further comprising:obtaining a difference between a target position of the stage and anactual position thereof to apply, across electrodes for deflecting theelectrons, a correction voltage operable to cancel the obtaineddifference.
 13. The method of claim 1, wherein the secondary electronscomprises any one of electrons produced from the substrate, reflectedelectrons and back scattered electrons.
 14. The method of claim 1,wherein the secondary electrons comprises mirror electrons reflected inthe vicinity of a surface of the substrate.